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🫀 CARDIOVASCULAR SYSTEM - EXAM CRUSH GUIDE

Pathology + Medicine Combined | Pattern-Based Memory Aids + Flowcharts

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🗺️ THE BIG PICTURE MAP (Start Here)

RISK FACTORS
(HTN, DM, Smoking, Hyperlipidemia, Family Hx)
        ↓
   ATHEROSCLEROSIS
   (Endothelial Injury → Foam Cells → Plaque)
        ↓
  ┌─────────┬──────────┬─────────┐
  ↓         ↓          ↓         ↓
 IHD    STROKE     PAD      ANEURYSM
(angina,MI)  (TIA,CVA)  (claudication) (aorta)
  ↓
MYOCARDIAL INFARCTION
  ↓
HEART FAILURE / ARRHYTHMIAS / SUDDEN DEATH

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⚡ MODULE 1 — ATHEROSCLEROSIS

Pathophysiology Flowchart (Robbins Basic Pathology)

ENDOTHELIAL INJURY (HTN, oxidized LDL, smoking, toxins)
         ↓
  Increased permeability → LDL enters intima
         ↓
  Monocytes migrate in → become MACROPHAGES
         ↓
  Macrophages engulf oxidized LDL → FOAM CELLS
         ↓
  Fatty streak (earliest visible lesion — reversible)
         ↓
  SMC migration from media → Intima
  SMC proliferation + ECM synthesis
         ↓
  FIBROUS PLAQUE (lipid core + fibrous cap)
         ↓
  Calcification, Necrosis, Inflammation
         ↓
  COMPLICATED PLAQUE
  ├── Stable: gradual stenosis → Stable angina
  └── Unstable: PLAQUE RUPTURE → Thrombosis → ACS/MI

Fatty streak → Oxidized LDL eaten → Atheroma forms → Macrophages become foam cells

• Plaque rupture (NOT stenosis) = most common cause of MI
• Fibrous cap is thin at shoulder regions = rupture-prone
• Stable plaque = thick cap, calcified, less lipid
• Vulnerable plaque = thin cap, large lipid core, lots of macrophages

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❤️ MODULE 2 — CARDIAC HYPERTROPHY → HEART FAILURE

Pathophysiology Flowchart (Robbins Cotran & Kumar)

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🔄 MODULE 3 — HEART FAILURE VICIOUS CYCLE

Compensatory Response Flowchart (Katzung Pharmacology)

The Vicious Spiral (MUST KNOW)

↓ Cardiac Output
    ↙              ↘
↓ Baroreceptor     ↓ Renal blood flow
  firing
    ↓                   ↓
↑ SNS discharge     ↑ Renin → ↑ Ang II → ↑ Aldosterone
    ↓                   ↓
↑ HR, contractility  ↑ Na+/H₂O retention
    ↓                   ↓
       ↑ PRELOAD + ↑ AFTERLOAD
              ↓
    MORE ↓ Cardiac Output  ← VICIOUS CYCLE
              ↓
    Remodeling (fibrosis, hypertrophy → dysfunction)

Renin-Angiotensin-Aldosterone-System causes vasoconstriction + fluid retention → worsens HF. Drugs that block RAAS (ACEi, ARB, MRA) break the cycle.

Left vs Right Heart Failure - "BACK UP" Pattern

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💥 MODULE 4 — MYOCARDIAL INFARCTION

Time-Based Pathology (The Classic Exam Sequence)

MI Complications - "DRESSLER + PUMP"

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🌡️ MODULE 5 — SYSTOLIC vs DIASTOLIC HF

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💊 MODULE 6 — DRUG TARGETS IN HF (Med School Killer Topic)

The Targets Map

         NEUROHUMORAL AXIS
              ↓
    ┌─────────┴──────────┐
    SNS                 RAAS
  β1-receptor        ACE/AT1 receptor
     ↓                    ↓
  β-BLOCKERS           ACEi / ARBs
(carvedilol,           (enalapril,
 metoprolol)           sacubitril/valsartan)
                         ↓
                    Aldosterone
                         ↓
                  MRA (spironolactone,
                       eplerenone)

  FLUID OVERLOAD → DIURETICS (furosemide, HCTZ)
  GLUCOSE pathway → SGLT2i (dapagliflozin) ← NEW 1st line
  
  INOTROPES (acute only): Dobutamine (β1), Milrinone (PDE3i)
  VASODILATORS: Nitrates (↓ preload), Hydralazine (↓ afterload)
  DIGOXIN: ↑ contractility (Na/K-ATPase inhibitor) — narrow TI

ACEi/ARB (or sacubitril-valsartan) | Beta-blocker | MRA (mineralocorticoid antagonist) | Big add: SGLT2 inhibitor

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🚦 MODULE 7 — ANGINA PATTERNS QUICK COMPARE

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🧠 MODULE 8 — VALVULAR DISEASE CHEAT SHEET

Stenosis vs Regurgitation Sound Pattern

Pulmonary/Aortic Stenosis = Systolic murmur Mitral/Tricuspid Stenosis = Diastolic murmur Regurgitation = OPPOSITE valve timing

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🔬 MODULE 9 — HIGH-YIELD PATHOLOGY BUZZWORDS

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📋 MODULE 10 — ONE-LINE MEMORY AIDS COLLECTION

Stenosis (aortic/mitral) | Arrhythmias | Dilated CMP | Left IHD | Ischaemia | Valve disease | Endocarditis | Septal defects

Carditis | Arthritis (migratory) | Sydenham's Chorea | Subcutaneous nodules | Erythema marginatum Minor: Fever, ↑ ESR/CRP, Prolonged PR interval Mnemonic = "CASES + FP"

Aspirin + Anticoagulant | Beta-blocker | Clopidogrel/P2Y12 inhibitor | Dual antiplatelet | Early PCI (door-to-balloon <90 min)

Delay (weeks later) | Dull chest pain | Diffuse ST elevation (pericarditis) | Diagnose with Echo | Drug = NSAIDs / Colchicine

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🏁 EXAM PATTERN RECOGNITION GUIDE

"What Does the Exam Give You?" Pattern Matching

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🫀 CARDIOVASCULAR PATHOPHYSIOLOGY — EXAM CRUSH MASTER GUIDE

IHD · CCF · Rheumatic Fever · Atheroma · Arteriosclerosis + More

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═══════════════════════════════════

PART 1 — ARTERIOSCLEROSIS & ATHEROMA

═══════════════════════════════════

🔷 1A. ARTERIOSCLEROSIS — 3 Types (The Forgotten Comparison)

         ARTERIOSCLEROSIS
      (Hardening of arteries)
              │
    ┌─────────┼─────────────┐
    ▼         ▼             ▼
ATHEROSCLEROSIS  ARTERIOLOSCLEROSIS  MONCKEBERG'S
(Large/medium     (Small arteries      MEDIAL
 arteries)         & arterioles)      CALCIFICATION
    │                  │                   │
Lipid plaque      2 sub-types:        Calcium deposits
in INTIMA        ① Hyaline (benign    in MEDIA of
                    HTN, DM)           medium arteries
                 ② Hyperplastic       NO atheroma
                    (malignant HTN)    NO lumen change
                    "Onion-skin"       CLINICALLY SILENT
                                       (incidental X-ray)

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🔷 1B. ATHEROMA (Atherosclerosis) — Complete Pathophysiology Flowchart

RISK FACTORS
┌─────────────────────────────────────────────┐
│ HTN · Smoking · DM · Hyperlipidemia         │
│ Obesity · Age · Male sex · Family Hx        │
└─────────────────────────────────────────────┘
                    ↓
         ENDOTHELIAL INJURY / DYSFUNCTION
         (Mechanical stress, oxidized LDL, toxins)
                    ↓
    ┌───────────────────────────────┐
    │  ↑ Permeability of intima     │
    │  LDL enters & oxidizes        │
    │  Monocytes adhere & migrate   │
    └───────────────────────────────┘
                    ↓
         FATTY STREAK (EARLIEST LESION)
         Macrophages engulf oxidized LDL
              → FOAM CELLS form
         T lymphocytes accumulate
                    ↓
         FIBROUS PLAQUE
         SMC migrate media → intima
         SMC proliferate + secrete ECM
         Lipid core + Fibrous cap forms
                    ↓
        COMPLICATED PLAQUE (ADVANCED)
   ┌────────────────────────────────────┐
   │ Calcification  Ulceration          │
   │ Haemorrhage    Thrombosis          │
   └────────────────────────────────────┘
        ↙                         ↘
STABLE PLAQUE              VULNERABLE PLAQUE
(Thick fibrous cap,         (Thin cap, large
 heavy calcification,        lipid core, many
 gradual stenosis)           macrophages)
        ↓                         ↓
   STABLE ANGINA            PLAQUE RUPTURE
                                  ↓
                          ACUTE THROMBOSIS
                                  ↓
                  ┌───────────────┬─────────────┐
                  ↓               ↓             ↓
              STEMI / MI      UNSTABLE      SUDDEN
                               ANGINA       DEATH

Atheroma Memory Aids:

Fat (dyslipidaemia) · Family history · Fags (smoking) · Fat (obesity) · Forty+ (age)

Fatty streak → Oxidised LDL phagocytosed → Accumulate in macrophages → Macrophages = FOAM cells

Lumen
─────────────────────────────
        FIBROUS CAP
   (Smooth muscle + collagen)
─────────────────────────────
       LIPID CORE
   (Cholesterol + necrotic
    debris + foam cells)
─────────────────────────────
   SHOULDER REGION ← Rupture-prone!
   (Macrophages, T cells, thin cap)
─────────────────────────────
        Media

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═══════════════════════════════════

PART 2 — ISCHEMIC HEART DISEASE (IHD)

═══════════════════════════════════

🔴 2A. IHD Master Flowchart

CORONARY ATHEROSCLEROSIS (90% of IHD)
          ↓
   ┌──────┴───────┐
   ↓              ↓
STABLE         UNSTABLE/RUPTURE
(Fixed stenosis  (Plaque rupture
 >70% lumen)      + thrombus)
   ↓              ↓
STABLE         ACUTE CORONARY
ANGINA         SYNDROMES (ACS)
               ┌──────┬──────┐
               ↓      ↓      ↓
           UNSTABLE  NSTEMI  STEMI
           ANGINA

🔴 2B. Oxygen Supply vs Demand — The Core Concept

MYOCARDIAL ISCHAEMIA occurs when:

 DEMAND > SUPPLY

DEMAND ↑ by:            SUPPLY ↓ by:
• ↑ Heart rate          • Stenotic artery (atheroma)
• ↑ Contractility       • Coronary spasm (Prinzmetal)
• ↑ Wall tension        • Thrombosis
• ↑ BP (afterload)      • Anaemia (↓ O₂ carrying)
• Hypertrophy           • Tachycardia (↓ diastolic
                          filling time)

🔴 2C. Angina Types — Side-by-Side Pattern

         STABLE          UNSTABLE        PRINZMETAL
         ANGINA          ANGINA          (VARIANT)
─────────────────────────────────────────────────────
CAUSE    Fixed plaque    Plaque rupture  Vasospasm
         (>70%)          + partial       (no fixed
                         thrombus        plaque needed)

TRIGGER  Exertion        Rest OR less    REST, often
                         exertion        nocturnal
                         than before

ECG      ST ↓ (during    ST ↓ / T-wave   ST ↑
         episode)        inversion       (transient!)

TROPONIN Negative        Often +ve       Usually –ve
         
RELIEF   Rest/GTN        Partial GTN     Ca-channel
                                         blockers

TREATMENT BB + Nitrates  DAPT + Heparin  Diltiazem/
          + CCB          + PCI           Verapamil

🔴 2D. MYOCARDIAL INFARCTION — Sequence of Events

The Time-Based Pathology Table (Exam Favourite)

TIME          GROSS                HISTOLOGY            KEY EXAM POINT
─────────────────────────────────────────────────────────────────────
0–4 hrs       NORMAL               Wavy/elongated        No change on
                                   fibres (EM)           H&E! (trick Q)
                                   No H&E change

4–12 hrs      Pale / dark          Coagulative           Earliest
              mottling             necrosis begins,      VISIBLE change
                                   pyknosis, loss        on H&E
                                   of striations

12–24 hrs     Pale / mottled       Neutrophil            Neutrophils
                                   infiltration          arrive
                                   (peak day 2–3)

1–3 days      YELLOW               Dense neutrophils,    Peak necrosis
              soft centre          nuclear debris        period

3–7 days      YELLOW, SOFT         Macrophages           ⚠ HIGHEST
              (most danger!)       phagocytose           RUPTURE RISK
                                   debris

1–3 wks       Red-grey rim         Granulation tissue    Angiogenesis
                                   (vascular +           begins
                                   fibroblasts)

>6 wks        White fibrous        Dense collagen        SCAR complete
              scar                 scar, no cells        Non-contractile

N-ormal · N-eutrophils · M-acrophages · G-ranulation · S-car

MI Complications Flowchart

ACUTE MI
│
├─ 0–24h:  ARRHYTHMIAS (VF = #1 early death)
│           ↑ K+ leaks from necrotic cells → VF
│
├─ 1–3d:   CARDIOGENIC SHOCK
│           Loss >40% LV myocardium
│           ↓CO → ↓BP → ↓organ perfusion
│
├─ 3–7d:   MECHANICAL COMPLICATIONS (softening phase)
│   ├──── FREE WALL RUPTURE → Haemopericardium → TAMPONADE
│   │      (sudden death; Beck's triad: ↓BP, ↑JVP, muffled sounds)
│   ├──── PAPILLARY MUSCLE RUPTURE → Acute MR
│   │      (sudden pulmonary oedema, holosystolic murmur → axilla)
│   └──── SEPTAL RUPTURE (VSD)
│          (harsh holosystolic murmur, step-up in RV O₂)
│
├─ Days–Weeks: MURAL THROMBUS
│           Adherent to endocardium of infarcted zone
│           Risk of systemic emboli (stroke, mesenteric ischaemia)
│
├─ 2–10wks: DRESSLER SYNDROME
│           Autoimmune pericarditis post-MI
│           Fever + pleuritic chest pain + friction rub
│           Treatment: NSAIDs / Colchicine
│
└─ Months:  VENTRICULAR ANEURYSM
            Persistent ST elevation on ECG
            Paradoxical systolic bulge
            Risk of thrombus + refractory HF

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═══════════════════════════════════

PART 3 — CONGESTIVE CARDIAC FAILURE (CCF)

═══════════════════════════════════

💙 3A. CCF Master Pathophysiology Flowchart

UNDERLYING CAUSE
┌─────────────────────────────────────────────────────┐
│ IHD · HTN · Valvular disease · Cardiomyopathy       │
│ Congenital · Myocarditis · Arrhythmia               │
└─────────────────────────────────────────────────────┘
                     ↓
          ↓ MYOCARDIAL CONTRACTILITY
          or ↑ WORKLOAD (pressure/volume)
                     ↓
             ↓ CARDIAC OUTPUT
                     ↓
         ┌───────────┴──────────┐
         ▼                      ▼
  ↓ Baroreceptor           ↓ Renal Perfusion
  firing (carotid)              ↓
         ↓                 ↑ Renin → Ang II
  ↑ Sympathetic            ↑ Aldosterone
  discharge                     ↓
  ↑ HR, contractility,     Na+/H₂O retention
  vasoconstriction              ↓
         ↓                 ↑ Circulating volume
         └─────────┬────────┘
                   ↓
          ↑ PRELOAD + ↑ AFTERLOAD
                   ↓
         CARDIAC HYPERTROPHY/DILATION
                   ↓
         FURTHER ↓ CARDIAC OUTPUT
                   ↓
              VICIOUS CYCLE → DEATH

💙 3B. LEFT vs RIGHT Heart Failure Flowchart

LEFT HEART FAILURE              RIGHT HEART FAILURE
(Most common: IHD, HTN)         (Most common CAUSE = Left HF!)
         ↓                                ↓
LV cannot pump forward          RV cannot pump forward
         ↓                                ↓
Blood backs up into             Blood backs up into
PULMONARY CIRCULATION           SYSTEMIC VENOUS circulation
         ↓                                ↓
Pulmonary venous HTN            ↑ Systemic venous pressure
         ↓                                ↓
Pulmonary oedema                Peripheral oedema
                                Hepatomegaly / ascites
SYMPTOMS:                       SYMPTOMS:
• Dyspnoea on exertion          • Pitting oedema (legs)
• Orthopnoea (2+ pillows)       • JVP elevation
• Paroxysmal nocturnal          • Hepatomegaly (tender)
  dyspnoea (PND)                • Ascites
• Pink frothy sputum            • Anorexia / nausea
• Fine crackles (lungs)         • Engorged neck veins

PATHOLOGY:                      PATHOLOGY:
• Heavy wet lungs               • Nutmeg liver
• Heart failure cells           • Congestive
  (haemosiderin-laden             splenomegaly
  macrophages)                  • Peripheral oedema
• Pulmonary oedema

Lasix (furosemide) · Morphine · Nitrates · Oxygen · Posture (sit upright)

💙 3C. Systolic vs Diastolic HF (HFrEF vs HFpEF)

              HFrEF                    HFpEF
           (Systolic)               (Diastolic)
─────────────────────────────────────────────────
EF         < 40%                    ≥ 50%

PROBLEM    Can't SQUEEZE            Can't RELAX
           (↓ contractility)        (↑ stiffness)

CAUSE      MI, Dilated CMP,         HTN, HCM,
           Myocarditis,             Old age, DM,
           Alcohol, Viral           Amyloid

WALL       Thin + Dilated           Thick + Stiff
           (Eccentric hypertrophy)  (Concentric hypertrophy)

Rx TARGET  Reduce remodelling:      Rate control,
           ACEi + BB + MRA +        Diuretics
           SGLT2i                   (treat cause)

INOTROPES? YES (in acute)           NO (may worsen)

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═══════════════════════════════════

PART 4 — RHEUMATIC FEVER & RHD

═══════════════════════════════════

🟡 4A. Pathogenesis Flowchart (Molecular Mimicry)

Group A Streptococcus (GAS)
pharyngitis
         ↓
  2–3 week latent period
  (Antibody production time)
         ↓
Antibodies to Streptococcal M protein
CROSS-REACT with cardiac antigens
         ↓
  ┌──────────────────────────────┐
  │  Molecular Mimicry           │
  │  (Strep M protein ≈ cardiac  │
  │   sarcolemmal proteins)      │
  └──────────────────────────────┘
         ↓
T cell + Antibody-mediated
IMMUNE ATTACK on heart
         ↓
PANCARDITIS = Pericarditis
           + Myocarditis
           + Endocarditis
         ↓
ASCHOFF BODIES in myocardium
(pathognomonic!)
         ↓
With repeated attacks:
CHRONIC RHEUMATIC HEART DISEASE

🟡 4B. Acute Rheumatic Fever — JONES CRITERIA

JONES CRITERIA (Diagnosis requires 2 MAJOR or 1 MAJOR + 2 MINOR)
+ Evidence of preceding GAS infection

MAJOR CRITERIA              MINOR CRITERIA
("CASE C")                  ("FFFPPP")
─────────────────────────────────────────────────────
C arditis                   F ever
A rthritis (migratory,      F↑ ESR / CRP
  large joints — "flitting") P rolonged PR interval
S ydenham's Chorea           (1st degree AV block)
  ("St Vitus' dance")
E rythema Marginatum
  (skin — macular, central
   clearing, like a map)
S ubcutaneous Nodules
  (over bony prominences)

PLUS: Evidence of GAS infection
• ↑ ASO titre · Throat culture · Recent scarlet fever

Carditis · Arthritis · Sydenham's chorea · Erythema marginatum · Subcutaneous nodules + Fever · Prolonged PR

🟡 4C. Pathology — Morphological Features

ACUTE RHD                    CHRONIC RHD
─────────────────────────────────────────────────
ASCHOFF BODIES               VALVE SCARRING
• Myocardial foci of         • Fibrous thickening
  T-lymphocytes +             of leaflets
  plasma cells +             • Commissural fusion
  ANITSCHKOW cells           • Chordae thickening
  ("caterpillar cells")        and fusion
                             
VERRUCAE                     FISH-MOUTH / BUTTON-
• Small 1–2mm vegetations     HOLE STENOSIS
  on valve line of closure   (mitral valve — classic)
  (ALONG closure line,
  unlike IE which is on      NEOVASCULARISATION
  leaflet surface)            of valve leaflets

MACCALLUM PLAQUE             VALVES AFFECTED:
• Left atrial subendo-       Mitral > Mitral+Aortic
  cardial thickening          > Tricuspid (rare)

🟡 4D. RHD → Mitral Stenosis Chain

Repeated RF episodes
         ↓
Mitral valve leaflet fusion + thickening
         ↓
MITRAL STENOSIS (RHD = virtually ONLY cause)
         ↓
"Fish mouth" / "button hole" valve orifice
         ↓
↑ LA pressure → LA ENLARGEMENT
         ↓
   ┌─────┴──────┐
   ↓            ↓
ATRIAL        PULMONARY
FIBRILLATION  HYPERTENSION
(risk of LA     ↓
 thrombus +  Right heart
 embolism)   failure (cor pulmonale)

Opening Snap (OS) after S2
     +
Mid-diastolic rumbling murmur (at apex)
     +
Loud S1 (due to valve snapping shut)
= MITRAL STENOSIS (rheumatic)

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═══════════════════════════════════

PART 5 — CARDIOMYOPATHIES (Bonus High-Yield)

═══════════════════════════════════

🟣 The 3 Types — Pattern Table

         DILATED (DCM)    HYPERTROPHIC (HCM)   RESTRICTIVE (RCM)
──────────────────────────────────────────────────────────────────
PATHOLOGY  Dilation +        Asymmetric septal    Stiff myocardium
           systolic dysfun.  hypertrophy          Diastolic dysfun.

CAUSE      Idiopathic (40%)  GENETIC (AD)         Amyloid, sarcoid,
           Alcohol, viral    MYH7 / MYBPC3        haemochromatosis
           myocarditis,      mutation             eosinophilia
           peripartum

SHAPE      Dilated,          Thick                Normal size /
           thin walls        asymmetric           slightly enlarged
                             septum               stiff wall

OUTFLOW    Normal            OBSTRUCTION          Normal
           (until late)      (HOCM — LVOTO)

MURMUR     S3 gallop         Systolic ejection    ↑ JVP, ↓ pulse
                             murmur               pressure

KEY Rx     ACEi + BB +       BB / Verapamil       Treat cause
           Diuretics         Avoid inotropes!     Diuretics (careful)
           SGLT2i            ICD if at risk

EXAM CLUE  Young patient     Young athlete        Congo red +
           + AF + dilated    + syncope +          birefringence
           LV on echo        septal hypertrophy   = AMYLOID

"Young athlete drops dead OR syncopes on exertion + systolic murmur that INCREASES with Valsalva/standing, DECREASES with squatting/leg raise"

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═══════════════════════════════════

PART 6 — ENDOCARDITIS COMPARISON

═══════════════════════════════════

🔶 Endocarditis Types — Quick Pattern

          INFECTIVE (IE)      RHEUMATIC     LIBMAN-SACKS    MARANTIC
                                (RHD)          (SLE)        (Terminal)
──────────────────────────────────────────────────────────────────────
VEGETAT.  LARGE, irregular,    Small (1–2mm)  Small, sterile, Small, sterile
SIZE      friable              along closure  on BOTH sides  multiple
                               line           of leaflet

LOCATION  Atrial surface of    Closure line   Both surfaces  Any valve
          AV valves;           of mitral      of mitral
          ventricular          valve          valve
          surface of
          semilunar

ORGANISM  Strep viridans       NONE           NONE           NONE
          (dental); Staph      (immune)       (immune)       (debilitating
          aureus (IV drug);                                   illness)
          Strep bovis
          (colon cancer link!)

KEY EXAM  Roth spots,          Aschoff        SLE patient,   Cancer/
FEATURES  Osler nodes,         bodies,        antiphospholipid cachexia
          Janeway lesions,     caterpillar    syndrome       patient
          splinter haemorrhages cells, mitral
                               stenosis

Fever · Roth spots (retina) · Osler nodes (painful, fingers) · Murmur · Janeway lesions (painless palms) · Anaemia · Nail (splinter haemorrhages) · Emboli (septic)

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═══════════════════════════════════

PART 7 — TREATMENT FLOWCHARTS

═══════════════════════════════════

💊 STEMI Management — "TIME = MUSCLE"

STEMI Diagnosed (ST elevation + symptoms)
         ↓
   IMMEDIATE (within 10 minutes):
   Aspirin 300mg + P2Y12 inhibitor (ticagrelor/clopidogrel)
   + Anticoagulation (heparin/fondaparinux)
   + O₂ only if SpO₂ <94%
   + GTN if no hypotension
         ↓
   REPERFUSION STRATEGY:
   ┌─────────────────────────────┐
   │  PCI available?             │
   │  YES → Primary PCI          │
   │        (door-to-balloon     │
   │         <90 mins)           │
   │  NO → Thrombolysis          │
   │        (within 12h onset)   │
   │        Streptokinase/       │
   │        Alteplase            │
   └─────────────────────────────┘
         ↓
   SECONDARY PREVENTION:
   DAPT (12 months)
   Beta-blocker (reduce remodelling)
   ACEi/ARB (reduce remodelling, ↓ mortality)
   Statin (stabilise plaque, ↓ LDL)
   +/– Eplerenone (if EF <40%)

💊 CCF/HFrEF Treatment — The "A-BOMB" Rule

ALL HFrEF PATIENTS (EF <40%) get:

A — ACEi (or ARB, or sacubitril/valsartan)
    ↓ Afterload, ↓ remodelling, ↓ mortality

B — Beta-Blocker (carvedilol, bisoprolol, metoprolol)
    ↓ HR, ↓ remodelling, ↓ sudden death
    
M — MRA (spironolactone or eplerenone)
    ↓ Aldosterone effects, ↓ fibrosis
    
+SGLT2 inhibitor (dapagliflozin / empagliflozin)
    New 1st line — reduces HF hospitalisation

+ DIURETICS for symptoms (furosemide for oedema)

For refractory/advanced HF:
+ Ivabradine (if HR >70 in sinus rhythm)
+ Hydralazine + Isosorbide dinitrate (if ACEi intolerant)
+ ICD (if EF <35% despite 3 months Rx)
+ CRT (if LBBB + EF <35%)

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═══════════════════════════════════

PART 8 — ONE-PAGE BUZZ-WORD MAP

═══════════════════════════════════

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═══════════════════════════════════

PART 9 — EXAM PATTERN RECOGNITION

═══════════════════════════════════

QUESTION GIVES YOU:               THINK:
──────────────────────────────────────────────────────────
Young + sore throat + 3 wks later  RHEUMATIC FEVER
fever, migratory arthritis,         (Jones criteria!)
carditis

↑ ASO titre + 1st degree AV block  RF minor criteria
+ fever

Mid-diastolic rumble + opening snap MITRAL STENOSIS
+ AF + history of RF                (RHD)

Acute MI + day 5 + sudden           PAPILLARY MUSCLE
holosystolic murmur + pulmonary     RUPTURE → acute MR
oedema

Acute MI + day 5 + harsh            VENTRICULAR SEPTAL
holosystolic murmur + right heart   RUPTURE (VSD)
strain + step-up in RV O₂

Acute MI + sudden drop in BP +      FREE WALL RUPTURE
JVP rising + muffled sounds         → TAMPONADE

Persistent ST elevation 3 months    VENTRICULAR
post-MI + paradoxical wall motion   ANEURYSM

Young athlete + syncope +           HCM (HOCM)
↑ murmur with Valsalva

Fever + new murmur + IV drug user   INFECTIVE
or recent dental work               ENDOCARDITIS
+ Osler nodes + Roth spots

SLE patient + valve vegetations     LIBMAN-SACKS
on both sides                       ENDOCARDITIS

Elderly + calcific aortic stenosis  NORMAL WEAR
(crescendo-decrescendo murmur       (NOT rheumatic)
radiating to neck)

Marfan / Syphilis patient +         AORTIC
early diastolic murmur              REGURGITATION

---

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🫁 RESPIRATORY SYSTEM — EXAM CRUSH MASTER GUIDE

Pathology + Medicine Combined | Smart Flowcharts + Real Formulas

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THE MASTER MAP — RESPIRATORY DISEASE TREE

═══════════════════════════════════════

RESPIRATORY DISEASE
         │
    ┌────┴────────────────────────────┐
    ▼                                 ▼
OBSTRUCTIVE                      RESTRICTIVE
(↓ FEV1/FVC ratio)               (↓ FVC, normal ratio)
    │                                 │
    ├── Asthma                    ┌───┴─────────────┐
    ├── COPD                      ▼                 ▼
    │   ├── Emphysema          INTRINSIC         EXTRINSIC
    │   └── Chronic Bronchitis  (lung itself)    (chest wall,
    ├── Bronchiectasis           • Fibrosis        pleura, neuro)
    └── Cystic Fibrosis          • Sarcoidosis    • Kyphoscoliosis
                                 • Pneumoconioses • Obesity
                                 • ARDS           • Neuromuscular

Obstructive = Air TRAPPED in = FEV1↓, FVC normal/↓, FEV1/FVC <0.70 Restrictive = Air KEPT OUT = FVC↓, FEV1↓, FEV1/FVC normal (>0.70)

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PART 1 — ASTHMA

═══════════════════════════════════════

🔵 1A. Pathophysiology Flowchart

TRIGGER (allergen, cold, exercise, NSAIDS, infection, stress)
         ↓
MAST CELL ACTIVATION (IgE cross-linking in atopic asthma)
         ↓
PHASE 1 — EARLY RESPONSE (mins)
┌─────────────────────────────────────────────────────────┐
│ Histamine, LTC4/D4/E4 (leukotrienes), PGD2 released    │
│ → Bronchospasm (smooth muscle contraction)              │
│ → Mucus hypersecretion                                  │
│ → Mucosal oedema + vascular leakage                     │
└─────────────────────────────────────────────────────────┘
         ↓
PHASE 2 — LATE RESPONSE (hours)
┌─────────────────────────────────────────────────────────┐
│ Eosinophils, T-helper 2 (Th2) cells recruited           │
│ IL-4, IL-5, IL-13 drive:                               │
│ → More eosinophil influx                               │
│ → Goblet cell hyperplasia (excess mucus)               │
│ → Subepithelial FIBROSIS (basement membrane thickening) │
│ → Airway smooth muscle hypertrophy                     │
└─────────────────────────────────────────────────────────┘
         ↓
AIRWAY REMODELLING (chronic, irreversible component)
• Smooth muscle hypertrophy
• Subepithelial fibrosis
• Goblet cell hyperplasia
• Mucus plug formation
         ↓
AIR TRAPPING → ↑ RV → ↑ FRC → "barrel chest" in severe
FEV1/FVC < 0.70 (OBSTRUCTIVE PATTERN, reversible!)

🔵 1B. Asthma Classification (For Treatment Targeting)

SEVERITY       FREQUENCY         FEV1         NIGHT Sx
─────────────────────────────────────────────────────────
Intermittent   <2 days/week      ≥80%         ≤2/month
Mild persistent >2 days/wk       ≥80%         3-4/month
Moderate pers.  Daily            60-80%       >1/wk
Severe persist. Continuous       <60%         Frequent

🔵 1C. Asthma Treatment Ladder ("SABA to Biologics")

STEP 1: SABA (salbutamol) PRN — mild intermittent
         ↓ if not controlled
STEP 2: Low-dose ICS (budesonide/beclomethasone) + SABA
         ↓
STEP 3: Low ICS + LABA (formoterol) OR medium ICS
         ↓
STEP 4: Medium/High ICS + LABA ± LTRA (montelukast)
         ↓
STEP 5: Add-on therapy:
         • Tiotropium (LAMA)
         • Biologics:
           - Omalizumab (anti-IgE — atopic asthma)
           - Mepolizumab (anti-IL-5 — eosinophilic)
           - Dupilumab (anti-IL-4Rα)
         ↓
ACUTE SEVERE: Nebulised SABA + ipratropium + IV steroids
              + IV MgSO₄ (muscle relaxant) + O₂

"SMART" regime = Single inhaler Maintenance And Reliever Therapy (ICS/formoterol for both maintenance and rescue)

Status Asthmaticus red flags — "SCAT": Silent chest · Cyanosis · Altered consciousness · Tachycardia >120 + paradoxical pulse = INTUBATE

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═══════════════════════════════════════

PART 2 — COPD (Emphysema + Chronic Bronchitis)

═══════════════════════════════════════

🟤 2A. COPD Master Pathophysiology Flowchart

CIGARETTE SMOKE / AIR POLLUTANTS / α1-ANTITRYPSIN DEFICIENCY
         ↓
Chronic inflammation in airways + alveoli
(Neutrophils, macrophages, CD8+ T cells)
         ↓
         ┌───────────────┬────────────────────┐
         ▼               ▼                    ▼
  PROTEASE/ANTI-    MUCUS GLAND          SMALL AIRWAY
  PROTEASE          HYPERTROPHY          INFLAMMATION
  IMBALANCE         + GOBLET CELL        + FIBROSIS
  (↑ elastase,      HYPERPLASIA
  ↓ α1-AT)
         ↓               ↓                    ↓
  ALVEOLAR WALL     EXCESS MUCUS         Narrowing,
  DESTRUCTION       PRODUCTION           obliteration
         ↓               ↓                    ↓
    EMPHYSEMA       CHRONIC               Airflow
  (loss of elastic   BRONCHITIS            obstruction
   recoil)           (productive
                      cough >3 months/yr
                      for 2 consecutive yrs)

🟤 2B. Emphysema vs Chronic Bronchitis — The Classic Comparison

              EMPHYSEMA ("Pink Puffer")    CHRONIC BRONCHITIS ("Blue Bloater")
─────────────────────────────────────────────────────────────────────────────
PATHOLOGY    Permanent alveolar           Mucus gland hyperplasia
             enlargement + wall           (Reid Index >0.5)
             destruction; no fibrosis     Goblet cell excess

TYPE         Centriacinar (smoking)       Airway disease (large + small)
             Panacinar (α1-AT deficiency)

MECHANISM    ↑ Elastase destroys          Mucus obstruction +
             elastic tissue               secondary infection

MAIN Sx      Dyspnoea (severe)            Chronic productive cough
             cough (mild)                 Dyspnoea (moderate)

APPEARANCE   Thin, pursed lips,           Overweight, cyanosed,
             barrel chest,                oedematous
             using accessory muscles      ("Blue Bloater")
             ("Pink Puffer")

PaO₂ / CO₂  Near normal (hyperventilates) PaO₂↓, PaCO₂↑
             ("Pink" = adequate O₂)        (hypercapnic)

CXR          Hyperinflated, flat          Dirty lungs, ↑ lung
             diaphragm, bullae            markings, cardiomegaly

SPIROMETRY   FEV1/FVC < 0.70 both; FEV1 ↓ (obstructive in both)

KEY PATH     EMPHYSEMA = HOLES in         BRONCHITIS = GUNK
MNEMONIC     alveoli (destroyed walls)    in airways (mucus)

Reid Index = Thickness of mucous gland / Thickness of bronchial wall Normal = 0.4; Chronic Bronchitis = >0.5

🟤 2C. COPD Treatment Flowchart

ALL COPD:
• Smoking cessation (ONLY thing that slows decline!)
• Pulmonary rehab
• Vaccinations (flu, pneumococcal)
• Supplemental O₂ if PaO₂ <55mmHg (prolongs life)

MILD (FEV1 >80%):    SABA/SAMA PRN
MODERATE:            LAMA (tiotropium) ± LABA
SEVERE:              LAMA + LABA + ICS
VERY SEVERE:         + Roflumilast (PDE4 inhibitor)
                     + Azithromycin (chronic prophylaxis)
                     Consider lung transplant / LVRS

ACUTE EXACERBATION (AECOPD):
• Nebulised SABA + SAMA (ipratropium)
• Systemic corticosteroids (prednisolone 5 days)
• Antibiotics if purulent sputum (amoxicillin/doxycycline)
• Controlled O₂: target SpO₂ 88-92%
  (avoid high O₂ in CO₂ retainers — hypoxic drive!)
• NIV (BiPAP) if pH <7.35 + PaCO₂ ↑
• Intubation if NIV fails

GOLD 1 (Mild):       FEV1 ≥80% predicted
GOLD 2 (Moderate):   FEV1 50-79%
GOLD 3 (Severe):     FEV1 30-49%
GOLD 4 (Very Severe): FEV1 <30%

All require: FEV1/FVC < 0.70 post-bronchodilator

---

═══════════════════════════════════════

PART 3 — PNEUMONIA

═══════════════════════════════════════

🟠 3A. Pneumonia Pathology Flowchart — Lobar vs Broncho

PNEUMONIA = Alveolar inflammation + consolidation
         ↓
   ┌─────┴──────────────────┐
   ▼                        ▼
LOBAR PNEUMONIA          BRONCHOPNEUMONIA
(One/more entire lobes)  (Patchy, bilateral, multifocal)

CAUSE: Strep pneumoniae   CAUSE: Staph, H.influenzae,
       (most common)             Klebsiella, mixed flora
                                 (elderly, hospitalized)
STAGES:
① CONGESTION (day 1-2):   PATTERN:
   Vascular engorgement,   Scattered areas around
   serous exudate          bronchioles
   Red, heavy lung         "Lobular" distribution

② RED HEPATISATION (2-4d): KEY DIFFERENCE:
   Fibrin + RBC + PMN       No distinct stages
   Liver-like consistency   More common in
   "Red lung"               immunocompromised,
                            infants, elderly
③ GREY HEPATISATION (4-8d):
   RBCs lyse, fibrin,
   macrophages dominate
   "Grey lung"

④ RESOLUTION (8-10d):
   Enzymatic digestion of
   exudate by macrophages
   → Complete recovery
   OR → COMPLICATIONS
         ↓
COMPLICATIONS:
• Pleural effusion / empyema
• Lung abscess (especially Klebsiella, Staph)
• Bacteraemia / Sepsis
• Respiratory failure
• Organisation → fibrous scarring

🟠 3B. Pneumonia Organisms by Pattern (Exam Formula)

COMMUNITY-ACQUIRED (CAP):
• "Typical" bacteria:
  - Streptococcus pneumoniae (most common overall)
    → Lobar consolidation, rusty sputum, single lobe
  - Haemophilus influenzae (COPD/smokers)
  - Klebsiella pneumoniae
    → Upper lobe, "currant jelly" sputum (alcoholics)
    → Bulging fissure on CXR (classic Q)

• "Atypical" (walk-in, minimal exam signs):
  - Mycoplasma pneumoniae → young adults, "walking pneumonia"
    Cold agglutinins positive
  - Legionella → Legionnaire's disease
    AC/water cooling towers; hyponatraemia!
    GI symptoms + pneumonia (atypical combination)
  - Chlamydophila pneumoniae → mild, young adults
  - Influenza virus → viral pneumonia, secondary bacterial

HOSPITAL-ACQUIRED (HAP) / VENTILATOR (VAP):
  • Gram negatives: Pseudomonas, Klebsiella, E.coli
  • Staph aureus (MRSA in ICU)
  
IMMUNOCOMPROMISED:
  • PCP (Pneumocystis jirovecii) → AIDS (CD4 <200)
    Bilateral interstitial pattern, ↑ LDH, silver stain
  • Aspergillus fumigatus → neutropaenic patients
    "Halo sign" on CT (angioinvasive)
  • CMV pneumonitis → transplant recipients

C — Confusion (new)
U — Urea >7 mmol/L
R — Respiratory rate ≥30/min
B — BP (systolic <90 or diastolic <60)
65 — Age ≥65

Score 0-1: Treat at home
Score 2:   Hospital admission
Score 3-5: ICU consideration

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PART 4 — TUBERCULOSIS (TB)

═══════════════════════════════════════

🟢 4A. TB Pathophysiology Flowchart

Mycobacterium tuberculosis INHALED
(droplet nuclei, <5 microns — reach alveoli)
         ↓
Phagocytosed by alveolar MACROPHAGES
         ↓
Mycobacteria SURVIVE inside macrophage
(inhibit phagosome-lysosome fusion)
         ↓
T cell activation → CELL-MEDIATED IMMUNITY
         ↓
CD4+ T cells → secrete IFN-γ
→ macrophage activation
→ EPITHELIOID MACROPHAGES
+ multinucleated LANGHANS GIANT CELLS
         ↓
GRANULOMA FORMATION
(Caseating granuloma = pathognomonic)
         ↓
     ┌───┴──────────────┐
     ▼                  ▼
CONTAINED             PROGRESSIVE
(Calcified Ghon       TB DISEASE
 focus → Ghon         ↓
 complex)        Cavitation of lung
Latent TB        Spread:
                 • Bronchogenic (within lung)
                 • Haematogenous
                   → Miliary TB (millet seed lesions)
                   → Meningitis, Pott's disease
                   → Adrenal (Addison's)
                 • Lymphatic

🟢 4B. Ghon Complex vs Ranke Complex

GHON FOCUS:
Subpleural caseating granuloma
(usually lower upper or upper lower lobe)
         ↓
GHON COMPLEX = Ghon focus + ipsilateral hilar lymph nodes
(primary TB — usually heals)
         ↓
Calcification → RANKE COMPLEX (healed primary TB)
         ↓
Reactivation (immunosuppression, HIV, malnutrition)
→ POST-PRIMARY / SECONDARY TB
   • Upper lobe apical/posterior segments (O₂ rich)
   • Fibrocavitary disease
   • Systemic: night sweats, weight loss, haemoptysis

🟢 4C. TB Treatment Formula

ALL DRUG-SENSITIVE TB:
INTENSIVE PHASE (2 months): RIPE
   R — Rifampicin
   I — Isoniazid (INH)
   P — Pyrazinamide
   E — Ethambutol

CONTINUATION PHASE (4 months): RI
   R — Rifampicin
   I — Isoniazid

Total = 6 months (2RIPE / 4RI)

Side effect MEMORY — "RIPE" adverse effects:
R — Red/orange urine; Rifampicin = CYP450 inducer (↑ drug metabolism)
I — INH: Peripheral neuropathy (give pyridoxine/B6!)
       Hepatotoxicity; SLOWS CYP450
P — Pyrazinamide: Hyperuricaemia (gout), hepatotoxicity
E — Ethambutol: Eye toxicity (optic neuritis → colour blind)
    "E for Eye"

2 months RIPE → 4 months RI = total 6 months

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PART 5 — PULMONARY EMBOLISM (PE)

═══════════════════════════════════════

🔴 5A. DVT→PE Flowchart (Virchow's Triad as Foundation)

VIRCHOW'S TRIAD
┌─────────────────────────────────────────────────────┐
│ STASIS        HYPERCOAGULABILITY   ENDOTHELIAL INJURY│
│ Immobility    Pregnancy, OCP,      Surgery, trauma,  │
│ Long travel   Malignancy,          IV cannula        │
│ HF, obesity   Factor V Leiden,                       │
│               Antiphospholipid Ab                    │
└─────────────────────────────────────────────────────┘
         ↓
   DVT (DEEP VEIN THROMBOSIS)
   Proximal leg (iliac/femoral/popliteal) = highest risk
         ↓
   Thrombus dislodges
         ↓
   Travels via IVC → Right heart → PULMONARY ARTERY
         ↓
   PULMONARY EMBOLISM
         ↓
   ┌──────────────────────────────────────────────┐
   │ Effects depend on SIZE of embolus:           │
   │                                              │
   │ MASSIVE PE (>50% obstruction):               │
   │  → ↑ RV afterload → RV failure              │
   │  → ↓ LV filling → ↓ CO → Shock              │
   │  → Sudden death                              │
   │                                              │
   │ SUBMASSIVE PE (RV dysfunction, stable BP)    │
   │  → RV dilatation on echo/CT                 │
   │  → Troponin rise, ↑ BNP                     │
   │                                              │
   │ SMALL PE:                                    │
   │  → Pulmonary infarction (if end-artery):     │
   │    Wedge-shaped pleural infarct              │
   │    Pleuritic chest pain + haemoptysis        │
   └──────────────────────────────────────────────┘

🔴 5B. PE Diagnosis — Wells Score (Formula)

WELLS SCORE (pre-test probability):
• Clinical signs of DVT (leg swelling/tenderness): +3
• Alternative diagnosis less likely than PE:       +3
• HR >100 bpm:                                     +1.5
• Immobilisation/surgery in past 4 wks:           +1.5
• Previous DVT/PE:                                 +1.5
• Haemoptysis:                                     +1
• Malignancy:                                      +1

Score >4 = HIGH probability → CT-PA
Score ≤4 = LOW probability → D-dimer first

D-dimer: High sensitivity, LOW specificity
  (negative rules OUT PE; positive → still need CT-PA)

🔴 5C. PE Management Flowchart

SUSPECT PE
         ↓
Haemodynamically UNSTABLE?
   ↓YES:                      ↓NO:
MASSIVE PE                  Wells Score + D-dimer
  ↓                              ↓
Thrombolysis                CT Pulmonary Angiogram
(tPA/streptokinase)         (CTPA) = GOLD STANDARD
OR surgical embolectomy          ↓
                          CONFIRMED PE → anticoagulate
                          LMWH → warfarin (INR 2-3)
                          OR DOAC (rivaroxaban/apixaban)
                          Duration:
                          • Provoked: 3 months
                          • Unprovoked: 6 months
                          • Cancer/recurrent: INDEFINITE

S wave in lead I
Q wave in lead III
T inversion in lead III
+ Sinus tachycardia (most common finding)
+ Right bundle branch block (RBBB)

---

═══════════════════════════════════════

PART 6 — LUNG CANCER

═══════════════════════════════════════

🔵 6A. Lung Cancer Types — The Pattern Grid

          SMALL CELL (SCLC)      NON-SMALL CELL (NSCLC)
          ─────────────────────────────────────────────────
                            Squamous Cell | Adenocarcinoma | Large Cell
LOCATION  Central            Central       Peripheral      Peripheral
ORIGIN    Neuroendocrine      Bronchial     Glandular       ?
          Kulchitsky cells    epithelium    cells
SMOKING   Strong              Strong        Moderate        Strong
LINK
SPREAD    EARLY metastasis    Late          Late            Late
          (surgical cure rare)
MARKERS   NSE, chromogranin   Cytokeratin,  TTF-1, CK7     Diagnosis
          ACTH, ADH           p63/p40       Napsin A        of exclusion
          (paraneoplastic!)
PARANEOP. SIADH (↓Na+)        PTHrP        Hypertrophic    Gynaecomastia
SYNDROME  Cushing's (ACTH)    (↑Ca²+)      osteoarthropathy
          Eaton-Lambert
          (myasthenic)

KEY EXAM  "Oat cell" on       Keratin       Most common    Commonest in
BUZZWORD  histology           pearls        overall;       non-smokers
          Cavitation rare     Cavitation    non-smoker +   and women
                              common        female

🔵 6B. Paraneoplastic Syndromes Formula

SCLC Paraneoplastic — "SCLC = 3 S's"
  ① SIADH → Hyponatraemia (↓Na+) → confusion, seizure
  ② Syndrome of ectopic ACTH → Cushing's
  ③ Syndrome Eaton-Lambert → Proximal muscle weakness
     (↑ with repeated use — OPPOSITE of myasthenia gravis)

Squamous Cell Carcinoma:
  PTH-related Peptide (PTHrP) → HYPERCALCAEMIA
  ("Squamous = Squeezes out Calcium")
  Symptoms: Bones (pain), Moans (depression), Groans (GI), 
            Stones (renal), Psychic (confusion)

Adenocarcinoma:
  HPOA (Hypertrophic Pulmonary Osteoarthropathy)
  → Periosteal new bone formation → clubbing + joint pain

SIADH (SCLC) · Cushing (SCLC) · Acanthosis nigricans (adenoCa) · Lambert-Eaton (SCLC) · PTH-rP/hypercalcaemia (Squamous)

---

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PART 7 — PLEURAL DISEASE

═══════════════════════════════════════

7A. Pleural Effusion — TRANSUDATE vs EXUDATE (Light's Criteria)

PLEURAL EFFUSION FOUND
         ↓
Apply LIGHT'S CRITERIA
(Exudate if ANY one of 3 is met):

① Pleural protein / serum protein  > 0.5
② Pleural LDH / serum LDH          > 0.6
③ Pleural LDH                       > 2/3 upper limit of normal serum LDH

TRANSUDATE                          EXUDATE
(Starling forces imbalance)         (Inflammation/tumour/infection)
─────────────────────────────────────────────────────────────────
Heart failure                       Pneumonia (parapneumonic)
Cirrhosis (↓ oncotic pressure)      Malignancy
Nephrotic syndrome                  TB
Hypothyroidism                      PE (can be either)
Constrictive pericarditis           Rheumatoid arthritis, SLE
Meig's syndrome                     Mesothelioma
(ovarian fibroma + R. effusion)

7B. Pneumothorax Types

SPONTANEOUS:
  Primary — young, tall, thin males (Marfan-like)
  Secondary — COPD, asthma, TB, cystic fibrosis

TENSION PNEUMOTHORAX (EMERGENCY):
Air enters pleura → cannot escape
         ↓
Progressive ↑ pressure in affected side
         ↓
TRACHEA DEVIATES AWAY from affected side
Mediastinum shifts
↓ BP (↓ venous return)
↑ JVP
ABSENT BREATH SOUNDS ipsilateral

TREATMENT: Immediate needle decompression
(2nd intercostal space, midclavicular line)
BEFORE CXR!
Then chest drain

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═══════════════════════════════════════

PART 8 — ABG INTERPRETATION FORMULA

═══════════════════════════════════════

8A. Step-by-Step ABG Interpretation

STEP 1: pH
  <7.35 = ACIDOSIS
  >7.45 = ALKALOSIS

STEP 2: PaCO₂ (respiratory component)
  ↑ CO₂ + Acidosis = RESPIRATORY ACIDOSIS (hypoventilation)
  ↓ CO₂ + Alkalosis = RESPIRATORY ALKALOSIS (hyperventilation)

STEP 3: HCO₃⁻ (metabolic component)
  ↓ HCO₃ + Acidosis = METABOLIC ACIDOSIS
  ↑ HCO₃ + Alkalosis = METABOLIC ALKALOSIS

STEP 4: Is there COMPENSATION?
  (Opposite system moves to restore pH toward normal)

STEP 5: Calculate A-a gradient if needed
  A-a Gradient = PAO₂ - PaO₂
  PAO₂ = (FiO₂ × 713) - (PaCO₂ / 0.8)
  Normal A-a: <15 mmHg (on room air)
  ↑ A-a = V/Q mismatch, diffusion problem, shunt
  Normal A-a = hypoventilation only

8B. Classic ABG Patterns in Respiratory Disease

DISEASE          pH    PaCO₂   PaO₂    HCO₃   A-a GRAD
──────────────────────────────────────────────────────────
Acute asthma      ↑     ↓       ↓      Normal   ↑
(early)           (resp alkalosis - hyperventilating)

Severe asthma     ↓     ↑       ↓      Normal   ↑
(tiring)          (resp acidosis - fatigue, CO₂ rising = DANGER!)

COPD (stable)     ↓     ↑       ↓       ↑       ↑
(chronic)         (compensated resp acidosis)

PE (acute)        ↑     ↓       ↓      Normal   ↑
                  (resp alkalosis - hyperventilating)

Pulmonary         ↓     ↓       ↓       ↓       ↑
fibrosis          (metabolic acidosis + low CO₂)

Normal            7.40  40      95+    24      <15

CO₂ ↑ → pH ↓ (acidosis) CO₂ ↓ → pH ↑ (alkalosis) Always think: CO₂ is an ACID gas

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═══════════════════════════════════════

PART 9 — RESTRICTIVE LUNG DISEASE

═══════════════════════════════════════

9A. Interstitial Lung Disease Overview

INTERSTITIAL LUNG DISEASE (ILD) / PULMONARY FIBROSIS

CAUSE CATEGORIES:
┌────────────────────────────────────────────────────┐
│ KNOWN CAUSES:          UNKNOWN CAUSES:             │
│ Drugs: methotrexate,   IPF (Idiopathic Pulmonary   │
│  amiodarone,           Fibrosis) — most common ILD │
│  bleomycin             NSIP (Non-specific IP)       │
│ Connective tissue:     COP (Cryptogenic Organ.P)   │
│  RA, SLE, scleroderma  DIP, LIP                    │
│ Occupational:                                       │
│  Asbestosis, silicosis,                             │
│  coal worker's         GRANULOMATOUS:               │
│ Hypersensitivity       Sarcoidosis                  │
│  pneumonitis           Extrinsic allergic alveolitis│
└────────────────────────────────────────────────────┘

PATHOPHYSIOLOGY:
Repeated alveolar injury
         ↓
Aberrant repair → TGF-β driven fibroblast activation
         ↓
Collagen deposition in alveolar walls
         ↓
↑ Stiffness → ↓ compliance → Restrictive pattern
↓ Diffusion capacity (DLCO↓) — key feature
         ↓
Hypoxia (V/Q mismatch + diffusion block)
         ↓
Pulmonary hypertension → Cor pulmonale

9B. Pneumoconioses — The Occupation Pattern

DISEASE          DUST           PATHOLOGY        KEY FINDING
────────────────────────────────────────────────────────────
Silicosis        Silicon        Nodular fibrosis  "Eggshell
                 dioxide        (upper lobe)      calcification"
                                                  (hilar nodes)
                 ↑ Risk of TB! ("silico-TB")

Coal Worker's    Coal dust      Simple CWP:       Progressive
Pneumoconiosis   (carbon)       Black macules     Massive
                                Complex CWP:      Fibrosis (PMF)
                                Massive fibrosis  "Black lung"

Asbestosis       Asbestos       Bilateral lower   Pleural plaques
                 fibres         lobe fibrosis     (pathognomonic)
                                (interstitial)    Ferruginous
                                                  bodies
                                ↑ Risk:           (asbestos bodies)
                                Mesothelioma,
                                Bronchogenic Ca

Berylliosis      Beryllium      Non-caseating     Similar to
                 (aerospace)    granulomas        Sarcoidosis

"Asbestos = two cancers":

1. Mesothelioma (pleural/peritoneal — almost pathognomonic!)
2. Bronchogenic carcinoma (synergistic with smoking × 50–90×!) "Asbestos alone = 5× lung cancer risk; Asbestos + smoking = 50× risk"

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═══════════════════════════════════════

PART 10 — ONE-PAGE EXAM PATTERN BOARD

═══════════════════════════════════════

Buzzword → Diagnosis Formula

---

RAPID-FIRE DRUG REVIEW (Respiratory)

DRUG              CLASS              USE              KEY SIDE EFFECT
─────────────────────────────────────────────────────────────────────
Salbutamol        β2 agonist (SABA)  Asthma rescue    Tremor, tachycardia
Salmeterol        β2 agonist (LABA)  Asthma/COPD      Never alone in asthma!
Tiotropium        LAMA               COPD (first-line) Dry mouth, urinary retention
Ipratropium       SAMA               COPD, acute Rx   Dry mouth
Beclomethasone    ICS                Asthma control   Oral candidiasis, dysphonia
Prednisolone      Systemic CS        Acute asthma/AECOPD  Cushing's (long-term)
Montelukast       LTRA (leukotriene  Asthma, rhinitis  Well tolerated
                  receptor antag.)
Omalizumab        Anti-IgE biologic  Severe atopic    Anaphylaxis (rare)
                                     asthma
Roflumilast       PDE4 inhibitor     Severe COPD      Nausea, weight loss, depression
Rifampicin        Anti-TB            TB RIPE          Red urine, CYP inducer
Isoniazid (INH)   Anti-TB            TB RIPE          Peripheral neuropathy → give B6
Ethambutol        Anti-TB            TB RIPE          Optic neuritis (visual check!)
Pyrazinamide      Anti-TB            TB RIPE          Hyperuricaemia, hepatotoxicity
Nintedanib        Anti-fibrotic      IPF              Diarrhoea, hepatotoxicity
Pirfenidone       Anti-fibrotic      IPF              Photosensitivity, GI

---

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🫁 RESPIRATORY SYSTEM — EXAM ANSWERS

Based on Your Study Guide (Edition 2007)

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═══════════════════════════════════

QUESTION 1

List Congenital Malformations of the Respiratory System + Cause/Predisposing Factors

═══════════════════════════════════

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═══════════════════════════════════

QUESTION 2

Symptoms and Signs of Upper Respiratory Infection + Infective Process

═══════════════════════════════════

Anatomy of Upper Respiratory Tract (URT)

Nose → Nasopharynx → Oral pharynx → Larynx → Upper trachea

Symptoms and Signs

Infective Process in the URT

PATHOGEN INHALED / CONTACT with mucosa
         ↓
Binds to mucosal epithelial receptors
(Rhinovirus → ICAM-1; Strep → pharyngeal epithelium)
         ↓
Local INNATE IMMUNE RESPONSE
• Mast cell degranulation → vasodilation + oedema
• Kinins → pain + ↑ vascular permeability
• Mucus hypersecretion by goblet cells
         ↓
ADAPTIVE IMMUNE RESPONSE (days 3–5)
• Lymphocyte infiltration
• IgA secretion (protective)
• Cytokine release → fever (IL-1, IL-6, TNF)
         ↓
RESOLUTION (viral, 7–10 days)
OR COMPLICATIONS:
• Bacterial superinfection (Strep, H.influenzae)
• Otitis media (Eustachian tube spread)
• Sinusitis (sinus ostia blocked → secondary infection)
• Peritonsillar abscess / Retropharyngeal abscess
• Laryngotracheobronchitis (Croup) — children

Viral (90%): Rhinovirus (#1), Coronavirus, RSV, Influenza, Parainfluenza Bacterial: Group A Strep (Strep pyogenes) — CAUSES RHEUMATIC FEVER if untreated!

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═══════════════════════════════════

QUESTION 3

Pathogenesis of: (a) Bronchial Asthma (b) COPD (c) Tuberculosis

═══════════════════════════════════

(a) BRONCHIAL ASTHMA — Pathogenesis

SENSITISATION PHASE (first exposure to allergen):
Allergen (dust mite, pollen, dander) inhaled
         ↓
Processed by dendritic cells → presented to T cells
         ↓
Th2 cell differentiation
         ↓
IL-4 → B cell class switching to IgE
         ↓
IgE binds to mast cells in bronchial mucosa
(SENSITISED — no symptoms yet)

CHALLENGE PHASE (re-exposure):
Allergen cross-links IgE on mast cells
         ↓
MAST CELL DEGRANULATION
         ↓
┌────────────────────────────────────────────────┐
│ EARLY RESPONSE (mins):                         │
│ Histamine → bronchospasm + oedema             │
│ Leukotrienes (LTC4, LTD4, LTE4) → prolonged  │
│ bronchospasm + mucus secretion                 │
│ PGD2 → bronchoconstriction                    │
└────────────────────────────────────────────────┘
         ↓
┌────────────────────────────────────────────────┐
│ LATE RESPONSE (6–12 hrs):                     │
│ Eosinophil infiltration (via IL-5)             │
│ Major Basic Protein from eosinophils →        │
│ epithelial DAMAGE                              │
│ Goblet cell hyperplasia → thick mucus         │
│ Subepithelial FIBROSIS                        │
└────────────────────────────────────────────────┘
         ↓
AIRWAY REMODELLING (long-term):
• Smooth muscle HYPERTROPHY
• Basement membrane thickening
• Mucus plugging
• Irreversible component

NET RESULT: Reversible airflow obstruction
FEV1/FVC < 0.70 (improves >12% with bronchodilator)
Triggered also by: exercise, cold air, NSAIDS, stress, infection

---

(b) COPD — Pathogenesis

CIGARETTE SMOKE (main cause, 90%)
+ Air pollution, occupational dust, α1-antitrypsin deficiency
         ↓
Inhaled particles activate MACROPHAGES in alveoli
         ↓
Macrophages release:
• IL-8, LTB4 → recruit NEUTROPHILS
• MMP (matrix metalloproteinases) → destroy ECM
         ↓
NEUTROPHILS release ELASTASE
         ↓
         ┌──────────────────────┐
         ▼                      ▼
EMPHYSEMA                CHRONIC BRONCHITIS
(Protease/anti-protease   (Mucus gland
 imbalance)               hypertrophy)
         │                      │
↑ Elastase destroys       ↑ Goblet cells
 alveolar walls           ↑ Mucus secretion
         │                      │
Permanent airspace        Productive cough
 enlargement             ≥3 months/yr × 2yrs
Loss of elastic recoil    Airway narrowing +
Air trapping              infection → AECOPD
         │                      │
         └──────────┬───────────┘
                    ▼
         IRREVERSIBLE AIRFLOW OBSTRUCTION
         FEV1/FVC <0.70 (NO reversal with BD)
                    ▼
         V/Q mismatch → HYPOXIA
                    ▼
         Pulmonary vasoconstriction
                    ▼
         PULMONARY HYPERTENSION
                    ▼
         COR PULMONALE (right heart failure)

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(c) TUBERCULOSIS — Pathogenesis

Mycobacterium tuberculosis INHALED
(droplet nuclei <5µm — reach alveoli directly)
         ↓
Phagocytosed by ALVEOLAR MACROPHAGES
         ↓
Mycobacteria SURVIVE by inhibiting
phagosome-lysosome fusion
(Lipoarabinomannan on cell wall = key virulence)
         ↓
Macrophages present antigen to CD4+ T cells
         ↓
Th1 response → IFN-γ secreted
         ↓
Macrophages ACTIVATED → become EPITHELIOID CELLS
Multinucleated LANGHANS GIANT CELLS form
(peripheral nuclei, horseshoe arrangement)
         ↓
GRANULOMA FORMATION
(collection of epithelioid macrophages
 + Langhans giant cells + lymphocytes
 + CENTRAL CASEATION NECROSIS)
         ↓
         ┌──────────────┐
         ▼              ▼
  CONTROLLED TB      PROGRESSIVE TB
  (adequate immunity) (immunosuppressed, HIV,
         ↓            malnutrition, DM)
  GHON FOCUS forms         ↓
  (subpleural         Central necrosis liquefies
   granuloma)         → CAVITATION of lung
         ↓                 ↓
  + Hilar LN →       Haematogenous spread:
  GHON COMPLEX        • MILIARY TB
  → calcifies =       • TB Meningitis
  RANKE COMPLEX       • Pott's disease (spine)
  (LATENT TB)         • Adrenal TB (Addison's)

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═══════════════════════════════════

QUESTION 4

Pathophysiological Changes in: (a) Pneumonia (b) Tuberculosis (c) Lung Carcinoma

═══════════════════════════════════

(a) PNEUMONIA — Pathophysiological Changes

ORGANISM reaches alveoli
(inhalation, aspiration, haematogenous spread)
         ↓
INNATE DEFENCE FAILURE
(overwhelms mucociliary clearance + alveolar macrophages)
         ↓
INFLAMMATORY RESPONSE in alveoli
         ↓
LOBAR PNEUMONIA STAGES:

STAGE 1 — CONGESTION (day 1–2):
• Vascular engorgement + serous fluid fills alveoli
• Bacterial multiplication
• Lung = RED, heavy, boggy

STAGE 2 — RED HEPATISATION (day 2–4):
• Alveoli filled with RBCs + Fibrin + PMN neutrophils
• Lung = SOLID, RED, liver-like texture
• "Hepatisation" — looks like liver on cut section

STAGE 3 — GREY HEPATISATION (day 4–8):
• RBCs lyse (→ grey/white colour)
• Fibrin + macrophages dominate
• Bacteria being cleared
• Lung = GREY, firm

STAGE 4 — RESOLUTION (day 8–10):
• Macrophages digest fibrin via enzymatic lysis
• Alveolar architecture PRESERVED (unlike fibrosis)
• Complete return to normal
OR → COMPLICATIONS (empyema, abscess, fibrosis)

PATHOPHYSIOLOGICAL CONSEQUENCES:
• Consolidation → ↑ alveolar shunt → HYPOXIA
• V/Q mismatch → ↓ PaO₂
• Inflammatory cytokines → FEVER + systemic response
• Pleurisy if pleura involved → pleuritic chest pain
• SIADH (especially Legionella) → ↓ Na+

---

(b) TUBERCULOSIS — Pathophysiological Changes

PRIMARY TB:
Ghon focus → granuloma → caseation → fibrosis/calcification
↓ in lung function if large → restrictive pattern
Usually SILENT clinically

SECONDARY (POST-PRIMARY) TB:
Reactivation in UPPER LOBES (apical/posterior segments)
Why upper lobes? → Higher O₂ tension (Mycobacteria are aerobic)

PATHOPHYSIOLOGICAL CHANGES:
1. CAVITATION:
   • Caseous centre liquefies + drains into bronchus
   • Air enters → CAVITY forms
   • Cavity wall = fibrous + lined by necrotic debris
   • Mycobacteria multiply in cavity wall

2. BRONCHOGENIC SPREAD:
   • Infected material drains via bronchi
   • New foci in same/opposite lung

3. HAEMATOGENOUS SPREAD:
   • → Miliary TB: 1–2mm "millet seed" granulomas everywhere
   • → Brain (meningitis), bone (Pott's), kidney, adrenal

4. V/Q MISMATCH + FIBROSIS:
   • Destroyed lung tissue → restrictive + diffusion defect
   • Progressive respiratory failure

5. SYSTEMIC EFFECTS:
   • Cytokine (TNF-α) → fever, night sweats, weight loss
   • Cachexia (classic TB wasting = "consumption")
   • Haemoptysis from eroded vessels in cavity wall
   • Rasmussen's aneurysm = eroded pulmonary artery → massive haemoptysis

---

(c) LUNG CARCINOMA — Pathophysiological Changes

RISK FACTORS:
Smoking (#1) → polycyclic hydrocarbons + nitrosamines
→ DNA mutations in bronchial epithelium (RAS, p53, RB genes)
+ Asbestos, radon, occupational carcinogens
         ↓
CARCINOGENESIS (stepwise):
Normal epithelium → hyperplasia → metaplasia
→ dysplasia → carcinoma in situ → INVASIVE CARCINOMA
         ↓
TYPES AND LOCATION:
Central: Squamous cell + Small cell (arise in main/segmental bronchi)
Peripheral: Adenocarcinoma + Large cell (arise in periphery)
         ↓
LOCAL EFFECTS (Pathophysiology):

BRONCHIAL OBSTRUCTION:
Tumour occludes bronchus
→ Post-obstructive ATELECTASIS (collapse)
→ Post-obstructive PNEUMONIA (recurrent)
→ ↓ V/Q ratio in collapsed segment → HYPOXIA

INVASION:
• Pleura → Malignant pleural effusion (exudate)
• Superior Vena Cava → SVC syndrome
  (facial/arm oedema, distended neck veins)
• Sympathetic chain → Horner's syndrome
  (Ptosis, miosis, anhidrosis) — Pancoast tumour
• Recurrent laryngeal nerve → Hoarseness
• Pericardium → Malignant pericardial effusion
• Oesophagus → Dysphagia

PARANEOPLASTIC EFFECTS (systemic, without metastasis):
• SCLC + SIADH → Hyponatraemia
• SCLC + ectopic ACTH → Cushing's syndrome
• SCLC + Eaton-Lambert → Proximal muscle weakness
• Squamous cell + PTHrP → Hypercalcaemia
• Adenocarcinoma → HPOA (clubbing + periosteal new bone)

METASTATIC SPREAD:
Lymphatic → hilar + mediastinal nodes (→ SVC obstruction)
Haematogenous → Brain (epilepsy, headache)
             → Bone (pain, fracture, ↑Ca)
             → Liver (↑LFTs, jaundice)
             → Adrenal glands (Addison's)

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═══════════════════════════════════

QUESTION 5

Distinguish Pleural Effusion Secondary to TB vs Cancer of the Lung

═══════════════════════════════════

Summary Formula — "TB vs Malignant Effusion"

TB EFFUSION:                    MALIGNANT EFFUSION:
• Young patient                 • Older smoker
• Fever + night sweats          • Massive + bloodstained
• Lymphocytic exudate           • Cytology POSITIVE
• ↑ ADA (>40)                  • ADA normal
• AFB positive (sometimes)      • AFB negative
• Caseating granuloma           • Malignant cells on biopsy
  on biopsy                     
• Responds to anti-TB Rx        • Recurs rapidly after drainage

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🏥 MASTER MANAGEMENT FRAMEWORK

ABCDE + MONITOR + FOLLOW-UP

Applied to All Major Conditions

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THE UNIVERSAL SKELETON (from your card)

MANAGEMENT = ABCDE + SPECIFIC + MONITOR + FOLLOW-UP

A → Assess severity (ABC, scoring system)
B → Basic investigations to confirm
C → Conservative / General measures
D → Drugs (first line → second line → adjuncts)
E → Emergency procedures if needed
    +
    Monitor (vitals, labs, drug toxicity)
    +
    Follow-up (lifestyle, maintenance, education)

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═══════════════════════════════════

1. PNEUMONIA

═══════════════════════════════════

A — ASSESS SEVERITY
    CURB-65 Score:
    C = Confusion (new)
    U = Urea >7 mmol/L
    R = RR ≥30/min
    B = BP <90 systolic or <60 diastolic
    65 = Age ≥65
    ───────────────────────────────────
    Score 0–1: Treat at HOME (oral antibiotics)
    Score 2:   ADMIT to ward
    Score 3–5: HDU/ICU consideration

B — BASIC INVESTIGATIONS
    • CXR (consolidation — lobar/patchy)
    • FBC (↑WBC, ↑neutrophils)
    • CRP/ESR (elevated)
    • Sputum M/C/S + Gram stain + AFB (if TB suspected)
    • Blood cultures (×2 before antibiotics)
    • U&E, LFTs, glucose
    • ABG (if severe or SpO₂ <94%)
    • Urinary Legionella antigen (if atypical suspected)
    • Urinary pneumococcal antigen
    • Pulse oximetry + ECG

C — CONSERVATIVE / GENERAL MEASURES
    • Oxygen: Target SpO₂ 94–98%
      (88–92% if known CO₂ retainer/COPD)
    • IV fluids if dehydrated or septic
    • Analgesia for pleuritic chest pain
    • Bed rest + sitting upright
    • DVT prophylaxis (LMWH if admitted)
    • Nutritional support
    • Physiotherapy (chest physio if secretions)

D — DRUGS
    FIRST LINE (Community-Acquired Pneumonia):
    • Mild–Moderate: Amoxicillin 500mg TDS PO
      (+ Clarithromycin if atypical suspected)
    • Severe CAP: IV Co-amoxiclav + IV Clarithromycin
    • Penicillin allergy: Doxycycline OR Moxifloxacin

    SPECIFIC ORGANISMS:
    • Legionella: Fluoroquinolone (levofloxacin)
    • Mycoplasma: Macrolide or Doxycycline
    • Klebsiella: Cephalosporin (cefuroxime) ± aminoglycoside
    • MRSA (HAP): Vancomycin or Linezolid
    • PCP (HIV/AIDS): Co-trimoxazole (high dose)
      ± Prednisolone if PaO₂ <70mmHg

    ADJUNCTS:
    • Antipyretics (paracetamol)
    • Bronchodilators if wheeze
    • Steroids (dexamethasone in severe CAP — recent evidence)

E — EMERGENCY PROCEDURES
    • If empyema: Chest drain (intercostal)
    • If respiratory failure: NIV → intubation + mechanical ventilation
    • If septic shock: Sepsis 6 bundle (see Sepsis section)
    • If lung abscess: Prolonged antibiotics ± surgical drainage

MONITOR:
    • Temperature, RR, HR, BP, SpO₂ daily
    • CRP trend (should fall by day 3)
    • WBC + U&E
    • Sputum culture results
    • Drug toxicity (renal function if aminoglycosides)
    • Repeat CXR at 6 weeks (to confirm resolution — EXCLUDE CANCER)

FOLLOW-UP:
    • 6-week CXR (mandatory — exclude underlying malignancy)
    • Vaccination: Pneumococcal + Annual influenza
    • Smoking cessation counselling
    • Ensure full antibiotic course completed

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═══════════════════════════════════

2. TUBERCULOSIS (TB)

═══════════════════════════════════

A — ASSESS SEVERITY
    • Active TB vs Latent TB (LTBI)
    • Smear-positive vs smear-negative
    • Drug-sensitive vs MDR-TB / XDR-TB
    • HIV status (CD4 count)
    • Miliary vs pulmonary vs extrapulmonary
    • WHO TB scoring / site of disease

B — BASIC INVESTIGATIONS
    • Sputum AFB smear (×3 early morning specimens)
    • Sputum culture + Drug sensitivity testing (DST)
      (Gold standard — results in 4–8 weeks)
    • GeneXpert MTB/RIF PCR (rapid, 2 hours)
      — detects TB AND Rifampicin resistance
    • CXR: Apical/upper lobe cavitation,
      hilar lymphadenopathy, miliary pattern
    • Mantoux test / IGRA (interferon gamma release assay)
    • HIV test (mandatory in all TB patients)
    • FBC, LFTs (baseline before starting RIPE)
    • Renal function
    • Visual acuity + colour vision (baseline — Ethambutol)
    • Lumbar puncture if meningitis suspected
    • CT/MRI if CNS or spinal TB

C — CONSERVATIVE / GENERAL MEASURES
    • ISOLATION (airborne precautions):
      Negative pressure room; N95 mask for staff
      Until sputum smear-negative (usually 2 weeks Rx)
    • Nutritional support (TB causes wasting)
    • Contact tracing (all household contacts screened)
    • Notification to public health (MANDATORY, notifiable disease)
    • Vitamin B6 (pyridoxine) 10mg/day with INH
      (prevents peripheral neuropathy)
    • Directly Observed Therapy (DOT) if adherence concern

D — DRUGS
    STANDARD 6-MONTH REGIMEN (drug-sensitive TB):
    ┌────────────────────────────────────────────────┐
    │ INTENSIVE PHASE — 2 months:                   │
    │ R — Rifampicin                                │
    │ I — Isoniazid (INH)                           │
    │ P — Pyrazinamide                              │
    │ E — Ethambutol                                │
    │ (Written as: 2RIPE or 2HRZE)                 │
    │                                               │
    │ CONTINUATION PHASE — 4 months:               │
    │ R — Rifampicin                                │
    │ I — Isoniazid                                 │
    │ (Written as: 4RI or 4HR)                     │
    │                                               │
    │ TOTAL = 6 months (standard)                  │
    │ TB Meningitis / Bone TB = 9–12 months        │
    └────────────────────────────────────────────────┘

    SIDE EFFECTS (MUST KNOW):
    R — Red urine (harmless); hepatotoxicity;
        CYP450 INDUCER (↓ OCP, warfarin, antiretrovirals)
    I — Peripheral neuropathy (give B6!);
        hepatotoxicity; SLOWS CYP450
    P — Hyperuricaemia (gout); hepatotoxicity;
        arthralgia
    E — Optic neuritis → red-green colour blindness
        "E for Eye" — CHECK VISION before + during

    LATENT TB (LTBI) TREATMENT:
    • 6 months Isoniazid (6H) OR
    • 3 months Rifampicin + Isoniazid (3RH)

    MDR-TB (resistant to R + I):
    Bedaquiline + Linezolid + newer regimens
    Duration 18–24 months

E — EMERGENCY PROCEDURES
    • Massive haemoptysis: Bronchial artery embolization
    • Tension pneumothorax (from TB cavity): Chest drain
    • TB meningitis: IV steroids (dexamethasone)
      + TB drugs (penetrating CNS: R, I, P, Streptomycin)
    • Respiratory failure: ICU support

MONITOR:
    • Monthly sputum smear/culture (check conversion)
    • LFTs monthly (hepatotoxicity — stop if ALT >5× normal)
    • Visual acuity (Ethambutol)
    • Uric acid (Pyrazinamide)
    • HIV viral load + CD4 if co-infected
    • Drug interactions (Rifampicin + ARVs)

FOLLOW-UP:
    • Treatment completion certificate
    • CXR at 6 months post-treatment
    • Screen all contacts (household/close)
    • BCG vaccination for unvaccinated contacts/children
    • Isoniazid preventive therapy for HIV+ contacts
    • Public health notification + contact tracing
    • Educate: complete course even when feeling well

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═══════════════════════════════════

3. BRONCHIAL ASTHMA

═══════════════════════════════════

A — ASSESS SEVERITY
    ACUTE ASTHMA:
    ┌──────────────────────────────────────────────────┐
    │ MODERATE:  PEFR 50–75%, SpO₂ >92%, talking     │
    │ SEVERE:    PEFR 33–50%, SpO₂ <92%, can't        │
    │            complete sentences, RR >25, HR >110  │
    │ LIFE-       PEFR <33%, SpO₂ <92%, silent chest, │
    │ THREATENING: cyanosis, confusion, PaCO₂ normal  │
    │              or ↑ (DANGER SIGN = tiring!)        │
    └──────────────────────────────────────────────────┘
    CHRONIC: BTS/GINA step classification

B — BASIC INVESTIGATIONS
    • PEFR (peak expiratory flow rate) — before + after BD
    • Spirometry: FEV1/FVC <0.70 + reversibility ≥12%
    • Pulse oximetry + ABG (if severe: ↓PaO₂, ↑PaCO₂ = danger)
    • CXR (exclude pneumothorax, pneumonia, foreign body)
    • FBC (eosinophilia in atopic asthma)
    • IgE level + Skin prick tests (identify allergens)
    • Sputum: eosinophils, Curschmann spirals, Charcot-Leyden crystals
    • Bronchial provocation test (methacholine) — for mild/exercise-induced
    • Allergy panel (RAST test)

C — CONSERVATIVE / GENERAL MEASURES
    • Sit patient upright
    • Oxygen: target SpO₂ 94–98%
    • Identify + REMOVE TRIGGER (allergen, drug, exercise)
    • Smoking cessation
    • Avoid NSAIDs + β-blockers (can precipitate attacks)
    • Breathing exercises / Buteyko technique
    • Written Asthma Action Plan

D — DRUGS
    ACUTE SEVERE ASTHMA:
    1st: Nebulised Salbutamol 2.5–5mg every 20 min
    +   Nebulised Ipratropium 0.5mg
    +   Oral/IV Prednisolone 40–50mg
    +   Controlled O₂
    +   IV MgSO₄ 1.2–2g over 20 min (if life-threatening)
    If not responding: IV Salbutamol or IV Aminophylline
    Last resort: Intubation + ventilation (avoid if possible)

    CHRONIC MANAGEMENT (BTS Steps):
    Step 1: SABA (Salbutamol) PRN only
    Step 2: + Low-dose ICS (Beclomethasone/Budesonide)
    Step 3: + LABA (Salmeterol/Formoterol)
            SMART therapy (ICS/Formoterol for relief + maintenance)
    Step 4: + LTRA (Montelukast) OR ↑ ICS dose
    Step 5: Biologics:
            Omalizumab (anti-IgE — atopic/allergic asthma)
            Mepolizumab (anti-IL-5 — eosinophilic asthma)
            Dupilumab (anti-IL-4Rα — type 2 inflammation)

E — EMERGENCY
    • Intubation + mechanical ventilation (life-threatening)
    • Heliox (helium-oxygen mixture) if severe obstruction
    • IV bicarbonate if severe acidosis

MONITOR:
    • PEFR twice daily (morning dip = poorly controlled)
    • Symptom diary + night waking frequency
    • Inhaler technique at every visit
    • Steroid side effects (ICS: oral candidiasis, dysphonia)
    • Growth in children on ICS

FOLLOW-UP:
    • Review 48h after acute attack
    • Written action plan given to patient
    • Annual review: control, triggers, spirometry
    • Allergen avoidance education
    • Flu + pneumococcal vaccination
    • Refer to specialist if step 4–5

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═══════════════════════════════════

4. COPD

═══════════════════════════════════

A — ASSESS SEVERITY
    GOLD Spirometric Staging (post-bronchodilator FEV1/FVC <0.70):
    GOLD 1: FEV1 ≥80%    (Mild)
    GOLD 2: FEV1 50–79%  (Moderate)
    GOLD 3: FEV1 30–49%  (Severe)
    GOLD 4: FEV1 <30%    (Very severe)

    ABCD Assessment Groups (symptoms + exacerbation history):
    mMRC dyspnoea scale + CAT score + exacerbation frequency

    AECOPD Severity:
    Mild: home treatment
    Moderate: hospital admission
    Severe: HDU/ICU + NIV

B — BASIC INVESTIGATIONS
    • Spirometry (gold standard for diagnosis — irreversible obstruction)
    • CXR: hyperinflation, flat diaphragm, bullae
    • ABG: PaO₂, PaCO₂ (baseline + during exacerbation)
    • FBC (polycythaemia from chronic hypoxia)
    • Sputum M/C/S (during exacerbation)
    • ECG + Echo (cor pulmonale assessment)
    • α1-antitrypsin level (if young, non-smoker, panacinar pattern)
    • HRCT chest (assess bullae, emphysema distribution)
    • 6-minute walk test (functional assessment)

C — CONSERVATIVE / GENERAL MEASURES
    • SMOKING CESSATION (#1 intervention — only thing that slows decline!)
    • Pulmonary rehabilitation (exercise training + education)
    • Nutritional support (COPD causes weight loss)
    • Influenza vaccine (annual)
    • Pneumococcal vaccine
    • Long-term O₂ therapy (LTOT) if:
      PaO₂ <55mmHg (7.3 kPa) at rest OR
      PaO₂ 55–60mmHg + pulmonary HTN/polycythaemia
      MINIMUM 15 hours/day — prolongs survival!
    • Target SpO₂ 88–92% (NOT 94–98% — hypoxic drive!)

D — DRUGS
    STABLE COPD:
    GOLD A (few symptoms, low risk): SABA or SAMA PRN
    GOLD B (more symptoms):          LAMA (Tiotropium) ± LABA
    GOLD E (high exacerbation risk): LAMA + LABA + ICS triple
    Additional:
    • Roflumilast (PDE4 inhibitor) — if FEV1 <50% + chronic bronchitis
    • Azithromycin 250mg 3×/week — prophylaxis in frequent exacerbators

    AECOPD:
    • Nebulised Salbutamol + Ipratropium (back-to-back)
    • Prednisolone 30–40mg × 5 days PO
    • Antibiotics (if purulent sputum/2 of 3 Anthonisen criteria):
      Amoxicillin / Doxycycline / Clarithromycin 5 days
    • Controlled O₂: SpO₂ 88–92%
    • NIV (BiPAP) if: pH <7.35 + PaCO₂ >6kPa (respiratory acidosis)
      — reduces need for intubation, reduces mortality

E — EMERGENCY
    • Intubation + mechanical ventilation (if NIV fails or contraindicated)
    • Treatment of pneumothorax (chest drain)
    • Lung volume reduction surgery (LVRS) — selected severe emphysema
    • Lung transplantation (end-stage, no other option)

MONITOR:
    • Spirometry annually (track FEV1 decline)
    • SpO₂ and ABG (during exacerbations)
    • Sputum colour/volume (early exacerbation warning)
    • Inhaler technique + compliance
    • BMI and nutritional status
    • Depression screening (common in COPD)

FOLLOW-UP:
    • 6-week review post-exacerbation
    • Annual spirometry + review medication
    • Pulmonary rehabilitation referral
    • Advance care planning (end-stage COPD)
    • Self-management plan (rescue pack: antibiotics + steroids at home)
    • Oxygen therapy review

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═══════════════════════════════════

5. MYOCARDIAL INFARCTION (MI / STEMI)

═══════════════════════════════════

A — ASSESS SEVERITY
    • STEMI vs NSTEMI vs Unstable Angina
    • Killip Classification (heart failure in MI):
      Killip I: No HF (mortality 6%)
      Killip II: Mild HF (S3, crackles) (mortality 17%)
      Killip III: Pulmonary oedema (mortality 38%)
      Killip IV: Cardiogenic shock (mortality 81%)
    • Grace Score (risk stratification in NSTEMI)

B — BASIC INVESTIGATIONS
    • 12-lead ECG (immediately! — diagnosis of STEMI)
      ST elevation ≥2mm in ≥2 contiguous leads
      New LBBB = treat as STEMI
    • Troponin I/T (high-sensitivity) — at 0h + 3h
      (NSTEMI: troponin + but no ST elevation)
    • FBC, U&E, glucose, lipid profile
    • Coagulation (before thrombolysis)
    • CXR (pulmonary oedema, cardiomegaly)
    • Echocardiogram (wall motion, EF, complications)
    • Coronary angiography (at PCI)
    • ABG if respiratory distress

C — CONSERVATIVE / GENERAL MEASURES
    • Bed rest initially (sit up if dyspnoeic)
    • Oxygen ONLY if SpO₂ <94%
      (Routine O₂ is HARMFUL in normoxic MI patients!)
    • IV access + continuous ECG monitoring
    • Morphine (pain relief — also reduces preload)
    • Antiemetic (metoclopramide — with morphine)
    • GTN sublingual (if no hypotension)
    • NPO (nil by mouth) pre-PCI

D — DRUGS (IMMEDIATE — "BATMAN"):
    B — Beta-blocker (oral metoprolol) — only if stable, no bradycardia
    A — Aspirin 300mg loading dose STAT
    T — Ticagrelor 180mg OR Clopidogrel (P2Y12 inhibitor)
    M — Morphine 2.5–5mg IV (+ antiemetic)
    A — Anticoagulant: LMWH (enoxaparin) or UFH or Fondaparinux
    N — Nitrates (GTN SL or IV if persistent pain + normal BP)

    SECONDARY PREVENTION (post-MI, long-term):
    • DAPT: Aspirin + Ticagrelor/Clopidogrel (12 months)
    • Beta-blocker (reduce remodelling + arrhythmia)
    • ACEi/ARB (reduce remodelling, ↓ mortality — especially EF <40%)
    • Statin (high-intensity: Atorvastatin 80mg) — plaque stabilisation
    • Eplerenone/Spironolactone (if EF <40%)

E — EMERGENCY REPERFUSION (TIME = MUSCLE):
    STEMI: PRIMARY PCI (preferred)
    Door-to-balloon time: <90 minutes (direct presentation)
                          <120 minutes (transferred)
    
    If PCI NOT available within 120 mins:
    THROMBOLYSIS (within 12 hours of onset):
    • Alteplase / Streptokinase / Tenecteplase
    Contraindications: Recent stroke, active bleeding,
    severe HTN, aortic dissection

    Other procedures:
    • Temporary pacing (complete heart block)
    • IABP/LVAD (cardiogenic shock)
    • Emergency CABG (failed PCI, left main disease)
    • Defibrillation (VF/pulseless VT)

MONITOR:
    • Continuous ECG (arrhythmias — VF peak in first hour)
    • Troponin at 6h, 12h (peak and fall)
    • Serial ECG (ST resolution post-PCI?)
    • Echo at 24–48h (EF, wall motion, complications)
    • BP, HR, urine output hourly
    • Blood glucose (DM patients — target 6–10 mmol/L)
    • INR if on warfarin

FOLLOW-UP:
    • Cardiac rehabilitation programme (6–8 weeks)
    • Echo at 6–8 weeks (check EF → consider ICD if <35%)
    • Risk factor control: BP, cholesterol, glucose, smoking
    • DAPT review at 12 months
    • Driving restrictions (1 month private, 6 weeks LGV)
    • Return to work advice
    • Sexual activity: when can climb 2 flights stairs without symptoms

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═══════════════════════════════════

6. SEPSIS

═══════════════════════════════════

A — ASSESS SEVERITY
    SEPSIS DEFINITIONS (Sepsis-3):
    • Infection + SOFA score ≥2
    SEPTIC SHOCK:
    • Sepsis + vasopressors needed + lactate >2 mmol/L
    qSOFA (bedside screening):
    ≥2 of: RR ≥22, altered mentation, SBP ≤100

    NEWS2 score, MEWS score

B — BASIC INVESTIGATIONS
    • Blood cultures ×2 (before antibiotics — within 1 hour!)
    • FBC (WBC ↑ or ↓, left shift)
    • CRP, Procalcitonin (PCT — bacterial sepsis marker)
    • Lactate (↑ = poor tissue perfusion → target <2 mmol/L)
    • U&E, creatinine (AKI common in sepsis)
    • LFTs, coagulation (DIC screen)
    • ABG (metabolic acidosis, hypoxia)
    • Urinalysis + urine M/C/S
    • CXR (source — pneumonia, pleural empyema)
    • Wound swabs, drain cultures (identify source)
    • Blood glucose
    • Echo (if endocarditis or cardiac source suspected)

C — CONSERVATIVE / GENERAL MEASURES (THE "SEPSIS 6" BUNDLE):
    Within 1 HOUR:
    ① Give HIGH FLOW O₂ (target SpO₂ >94%)
    ② Take BLOOD CULTURES (×2 peripheral ± central)
    ③ Give IV ANTIBIOTICS (broad spectrum, within 1 hour)
    ④ Give IV FLUID CHALLENGE (500mL crystalloid bolus)
    ⑤ Measure LACTATE (venous or arterial)
    ⑥ Measure URINE OUTPUT (insert urinary catheter)

    Additional:
    • Source CONTROL (drain abscess, remove infected line/catheter)
    • DVT prophylaxis (LMWH)
    • Stress ulcer prophylaxis (PPI)
    • Glycaemic control (target 6–10 mmol/L — avoid hypoglycaemia)
    • Nutritional support (early enteral feeding if possible)

D — DRUGS
    ANTIBIOTICS (within 1 hour — do NOT wait for cultures):
    Unknown source: Piperacillin-Tazobactam (Tazocin) IV
                    OR Meropenem if severe/resistant organisms
    Community source: Co-amoxiclav ± Clarithromycin
    HAP/VAP: Tazocin + Vancomycin (MRSA cover)
    Meningococcal: Ceftriaxone IV
    De-escalate when cultures available (antibiotic stewardship)

    VASOPRESSORS (if fluid-unresponsive, MAP <65mmHg):
    1st: Noradrenaline (Norepinephrine) — vasopressor of choice
    2nd: Add Vasopressin if noradrenaline >0.25mcg/kg/min
    3rd: Adrenaline (epinephrine) — refractory septic shock

    INOTROPE (if myocardial depression):
    Dobutamine (β1 agonist — ↑ contractility)

    STEROIDS:
    Hydrocortisone 200mg/day IV (if vasopressor-refractory shock)

    RENAL REPLACEMENT (if AKI + acidosis/fluid overload):
    Continuous veno-venous haemofiltration (CVVHF)

E — EMERGENCY PROCEDURES
    • Rapid Sequence Intubation (if GCS ≤8, respiratory failure)
    • Surgical debridement (necrotising fasciitis)
    • Percutaneous drain (intra-abdominal abscess)
    • Emergency laparotomy (perforated viscus)
    • ECMO (refractory septic cardiomyopathy)

MONITOR:
    • Hourly urine output (target >0.5mL/kg/hr)
    • Lactate at 2h and 6h (target clearance >10%)
    • MAP hourly (target ≥65mmHg)
    • Hourly GCS
    • Temperature + WBC trends
    • Blood cultures results (48–72h)
    • Procalcitonin (guide antibiotic duration)
    • Daily organ function: creatinine, LFTs, platelets

FOLLOW-UP:
    • ICU diary / rehabilitation
    • Psychology support (post-sepsis PTSD, cognitive impairment)
    • Source identification + long-term Abx if needed
    • Investigate for underlying immunosuppression (HIV, DM, malignancy)
    • Education to patient/family

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═══════════════════════════════════

7. STROKE

═══════════════════════════════════

A — ASSESS SEVERITY
    • FAST: Face/Arm/Speech/Time
    • NIH Stroke Scale (NIHSS) — severity 0–42
    • Glasgow Coma Scale
    • Time of onset (window for thrombolysis = 4.5 hrs)
    • Ischaemic vs Haemorrhagic (CANNOT thrombolyse haemorrhage!)

B — BASIC INVESTIGATIONS
    • URGENT CT head WITHOUT contrast
      (rules out haemorrhage before thrombolysis)
    • MRI brain + DWI (better for ischaemic stroke)
    • CT angiography (large vessel occlusion — for thrombectomy)
    • ECG (AF = cardioembolic cause)
    • 12-lead ECG + 24h holter
    • Echo (thrombus, PFO, valvular disease)
    • FBC, INR, APTT, glucose, U&E
    • Carotid Doppler USS (carotid stenosis)
    • Lipid profile, HbA1c
    • BP in both arms

C — CONSERVATIVE / GENERAL MEASURES
    • Admit to STROKE UNIT (reduces mortality by 20%)
    • Maintain airway (nursing 30° upright)
    • O₂ only if SpO₂ <94%
    • Glucose management (target 4–11 mmol/L)
    • AVOID aggressive BP lowering in first 24h
      (unless >220/120 or haemorrhagic/thrombolysis)
    • DVT prophylaxis (TED stockings + LMWH after 48h in ischaemic)
    • NG tube (if dysphagia — aspiration risk)
    • Swallow assessment before oral intake
    • Bladder care, pressure area care

D — DRUGS
    ISCHAEMIC STROKE:
    • Aspirin 300mg (within 24–48h of CT confirming ischaemia)
    • Clopidogrel (long-term antiplatelet — better than aspirin alone)
    • Statins (Atorvastatin 80mg)
    • Antihypertensives (start after 48–72h: ACEi/CCB/thiazide)
    • Anticoagulation (AF-related): DOAC after 1–2 weeks
      (Apixaban / Rivaroxaban / Dabigatran)
    • Warfarin if prosthetic valves

    HAEMORRHAGIC STROKE:
    • Reverse anticoagulation (Vitamin K + PCC if on warfarin)
    • Andexanet alfa (reversal for apixaban/rivaroxaban)
    • BP control: IV labetalol or nicardipine (target <140mmHg)
    • Nimodipine (subarachnoid haemorrhage only — prevent vasospasm)
    NO antiplatelets/anticoagulants initially!

E — EMERGENCY PROCEDURES
    ISCHAEMIC:
    • IV Alteplase (tPA) within 4.5 hours of onset
      (if no contraindications: no haemorrhage, BP <185/110, no surgery)
    • Mechanical THROMBECTOMY (endovascular) up to 24h
      (for large vessel occlusion — anterior or basilar)

    HAEMORRHAGIC:
    • Neurosurgical evacuation (cerebellar haematoma >3cm, hydrocephalus)
    • EVD (external ventricular drain) for hydrocephalus
    • Surgical clipping / coiling (ruptured aneurysm in SAH)

MONITOR:
    • Neurological observations every hour (GCS, pupils, limb power)
    • BP monitoring (4 hourly)
    • Blood glucose monitoring
    • Temperature (fever worsens outcome)
    • Dysphagia assessment (SALT)
    • DVT surveillance

FOLLOW-UP:
    • TIA clinic within 24h for TIA (ABCD2 score)
    • Stroke rehabilitation: Physio + OT + SALT + Psychology
    • Secondary prevention: antiplatelet/anticoagulant + statin + antihypertensive
    • Carotid endarterectomy (if carotid stenosis >70%)
    • Driving: CANNOT drive for 1 month (TIA) / 1 month (stroke)
    • Depression screening (post-stroke depression common)

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═══════════════════════════════════

8. ACUTE KIDNEY INJURY (AKI)

═══════════════════════════════════

A — ASSESS SEVERITY (KDIGO Staging):
    Stage 1: Creatinine ×1.5–1.9 baseline OR ↑ ≥26μmol/L
             Urine output <0.5mL/kg/hr for 6–12h
    Stage 2: Creatinine ×2.0–2.9 OR
             Urine output <0.5mL/kg/hr for ≥12h
    Stage 3: Creatinine ×3 OR ≥354μmol/L OR
             Urine output <0.3mL/kg/hr for ≥24h
             OR anuria ≥12h

B — BASIC INVESTIGATIONS
    • Serum creatinine + eGFR (serial measurements)
    • U&E (especially K+ — hyperkalaemia = emergency!)
    • Bicarbonate (metabolic acidosis)
    • FBC, bone profile (Ca²+, phosphate)
    • Urinalysis + urine M/C/S (infection? Haematuria?)
    • Urine:plasma creatinine ratio (pre-renal vs intrinsic)
    • CXR (pulmonary oedema — fluid overload)
    • Renal USS (obstruction? Size? Hydronephrosis?)
    • Urine protein:creatinine ratio
    • Serology if indicated (ANA, ANCA, anti-GBM — for GN)
    • ECG (hyperkalaemia — peaked T waves, wide QRS)

C — CONSERVATIVE / GENERAL MEASURES
    PRE-RENAL (commonest — hypovolaemia):
    • IV fluid resuscitation (crystalloid — 0.9% saline or Hartmann's)
    • Stop nephrotoxic drugs:
      NSAIDs, ACEi/ARBs, aminoglycosides, contrast media
    • Insert urinary catheter (measure urine output hourly)
    POST-RENAL (obstruction):
    • Urinary catheter (if bladder outlet obstruction)
    • Nephrostomy / ureteric stent (if ureteric obstruction)

D — DRUGS
    TREAT UNDERLYING CAUSE:
    • Sepsis: Antibiotics (avoid aminoglycosides)
    • Contrast nephropathy: IV hydration pre/post procedure
    • Myeloma: Chemotherapy + hydration
    • Vasculitis/GN: Immunosuppression (steroids + cyclophosphamide)

    MANAGE COMPLICATIONS:
    HYPERKALAEMIA (K+ >6.5 or ECG changes) — EMERGENCY!
    Step 1: 10mL 10% Calcium Gluconate IV (cardioprotection — stabilises membrane)
    Step 2: Insulin + Dextrose IV (shifts K+ into cells)
    Step 3: Salbutamol nebulisation (shifts K+ into cells)
    Step 4: Sodium bicarbonate (if acidotic)
    Step 5: Calcium Resonium (binds K+ in gut)
    Step 6: RRT (definitive removal)

    FLUID OVERLOAD:
    • Furosemide IV (if urine output maintained)
    ACIDOSIS:
    • NaHCO₃ (if pH <7.1)

E — EMERGENCY (INDICATIONS FOR RENAL REPLACEMENT THERAPY):
    "AEIOU":
    A — Acidosis (pH <7.1 refractory)
    E — Electrolytes (K+ >6.5 refractory)
    I — Intoxication (dialysable toxins: lithium, salicylates, methanol)
    O — Overload (fluid overload refractory to diuretics)
    U — Uraemia (symptoms: encephalopathy, pericarditis, bleeding)

MONITOR:
    • Urine output HOURLY (target >0.5mL/kg/hr)
    • U&E + creatinine daily (or more)
    • K+ twice daily (hyperkalaemia = most dangerous)
    • Fluid balance chart (strict)
    • Daily weight (fluid status)
    • ECG if K+ abnormal

FOLLOW-UP:
    • Review ALL medications (dose adjust for renal function)
    • Review eGFR at 3 months (CKD development?)
    • Nephrology referral if no recovery/underlying GN
    • Avoid nephrotoxins long-term
    • BP control + low-protein diet if progressing to CKD

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═══════════════════════════════════

THE UNIVERSAL MANAGEMENT TEMPLATE

(Use for ANY condition in your exam)

═══════════════════════════════════

┌────────────────────────────────────────────────────────────┐
│              MANAGEMENT OF [CONDITION]                     │
├────────────────────────────────────────────────────────────┤
│ A — ASSESS SEVERITY                                        │
│     → Use scoring system (CURB65 / GOLD / NIHSS / SOFA)   │
│     → Classify mild/moderate/severe                        │
├────────────────────────────────────────────────────────────┤
│ B — BASIC INVESTIGATIONS                                   │
│     → Bloods: FBC, U&E, CRP, LFTs, glucose, cultures      │
│     → Imaging: CXR/CT/USS                                  │
│     → Special: ECG, spirometry, echo, etc.                 │
├────────────────────────────────────────────────────────────┤
│ C — CONSERVATIVE / GENERAL                                 │
│     → O₂, positioning, IV access, fluids                  │
│     → Nutritional support, DVT prophylaxis                 │
│     → Remove precipitant/trigger                           │
├────────────────────────────────────────────────────────────┤
│ D — DRUGS                                                  │
│     → 1st line (most effective, first-choice)              │
│     → 2nd line (if 1st fails or contraindicated)           │
│     → Adjuncts (symptom control, prophylaxis)              │
├────────────────────────────────────────────────────────────┤
│ E — EMERGENCY PROCEDURES                                   │
│     → What to do if patient deteriorates?                  │
│     → Intubation / Surgery / Intervention                  │
├────────────────────────────────────────────────────────────┤
│ MONITOR                                                    │
│     → Vitals: HR, BP, RR, Temp, SpO₂, GCS                │
│     → Labs: relevant bloods (frequency depends on severity)│
│     → Drug toxicity monitoring                             │
├────────────────────────────────────────────────────────────┤
│ FOLLOW-UP                                                  │
│     → When to review (48h / 6wk / 3 months)               │
│     → Lifestyle: diet, exercise, smoking, alcohol          │
│     → Maintenance therapy                                  │
│     → Patient education + compliance                       │
│     → Vaccinations / Screening / Referrals                 │
└────────────────────────────────────────────────────────────┘

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📚 PATHOPHYSIOLOGY VOLUME 1

RESPIRATORY + CARDIOVASCULAR SYSTEMS

Made Easy · Smart · Real · Exam-Ready

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╔══════════════════════════════════════╗

║ SECTION A: RESPIRATORY SYSTEM ║

╚══════════════════════════════════════╝

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🌬️ UNIT 1 — THE BASICS: HOW BREATHING WORKS

Real-World Analogy First

Think of the lung as a balloon inside a box. The balloon = lung. The box = chest wall. When you expand the box (chest wall moves out, diaphragm moves down), the balloon inflates. Elastic recoil of the balloon tries to collapse it. The balance between these forces is what keeps your lungs open at rest.

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1A. Lung Volumes — The Complete Map

Maximum Inspiration ────────────────── TLC (Total Lung Capacity)
                    ↑ IRV              = ~6 L
                    │ (Inspiratory
                    │  Reserve Volume)
Resting Inspiration ──────────────────
                    ↕ TV               TV = Tidal Volume = 500 mL
                    │ (Tidal Volume)   (normal quiet breath)
Resting Expiration ──────────────────  FRC = FRC (Functional Residual Capacity)
                    ↓ ERV              FRC = ERV + RV = ~2.5 L
                    │ (Expiratory      (volume at end of quiet expiration)
                    │  Reserve Volume)
Maximum Expiration ──────────────────
                    RV (Residual Volume = ~1.2 L)
                    (air that CANNOT be expelled — keeps alveoli open)

TLC = TV + IRV + ERV + RV        = ~6 L
VC  = TV + IRV + ERV             = ~4.8 L (vital capacity)
FRC = ERV + RV                   = ~2.5 L
IC  = TV + IRV                   = ~3.5 L

FRC cannot be measured by spirometry alone!
(Need: helium dilution OR body plethysmography)

Tidal · IRV (above tidal) · RV (below ERV) · ERV (below tidal)

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1B. Compliance — The Lung's Stretchability

COMPLIANCE = ΔVolume / ΔPressure  (L/cmH₂O)

Normal lung compliance = 0.2 L/cmH₂O

HIGH compliance (too stretchy):    LOW compliance (too stiff):
• Emphysema                        • Pulmonary fibrosis
• Old age                          • ARDS
Lungs collapse EASILY              Lungs hard to inflate
Air TRAPPING                       ↑ Work of breathing

LOW compliance (fibrosis):           HIGH compliance (emphysema):
↑ Elastic recoil → lung collapses    ↓ Elastic recoil → no recoil
↑ Work to INFLATE                    → Air trapping, barrel chest
→ Restrictive pattern                → Obstructive pattern

Surfactant (from Type II pneumocytes):
• Phospholipid — lines alveolar surface
• ↓ Surface tension (by disrupting water molecule bonds)
• PREVENTS alveolar collapse (atelectasis)
• More effective in SMALL alveoli (LaPlace's law: P = 2T/r)
  → Without surfactant, small alveoli would empty into large ones

DEFICIENCY:
• Premature infants → Respiratory Distress Syndrome (IRDS/HMD)
• Hyaline membrane disease — pink hyaline membranes on histology
• Treat with: Exogenous surfactant (beractant) + CPAP

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1C. Ventilation and Perfusion — V/Q Ratio

V = Ventilation (air reaching alveoli) — ~4 L/min
Q = Perfusion (blood flow to alveoli)  — ~5 L/min

NORMAL V/Q ratio = 0.8  (slightly more perfusion than ventilation)

KEY PRINCIPLE: For gas exchange to work, V and Q must MATCH

APEX (top of lung):               BASE (bottom of lung):
• V > Q                           • Q > V
• V/Q = HIGH (>1)                 • V/Q = LOW (<1)
• Better ventilated per unit      • Better perfused per unit
  blood flow                        air flow
• TB prefers apex! (why?)         • Pneumonia more common
  → High O₂ tension at apex         at bases
  → Mycobacteria are aerobic

NORMAL V/Q:            V/Q = 0.8     Good gas exchange ✓

LOW V/Q MISMATCH:      V/Q < 0.8     Perfusion without ventilation
(SHUNT-like)                         Blood passes through, not oxygenated
                                     Cause: Pneumonia, pulmonary oedema,
                                     atelectasis, mucus plugging
                                     → Hypoxia, responds POORLY to O₂

HIGH V/Q MISMATCH:     V/Q > 0.8     Ventilation without perfusion
(DEAD SPACE-like)                    Air moves but no blood to exchange
                                     Cause: Pulmonary embolism
                                     → Wasted ventilation, ↑PaCO₂ risk

TRUE SHUNT:            V/Q = 0       No ventilation at all
                                     Blood bypasses lung entirely
                                     Cause: Atelectasis, ARDS, cardiac shunt
                                     → Hypoxia, does NOT respond to O₂
                                        (This is the KEY exam point!)

DEAD SPACE:            V/Q = ∞       No perfusion at all
                                     Air ventilates but no blood
                                     Cause: PE, low cardiac output

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1D. Gas Exchange — Oxygen and CO₂

OXYGEN DELIVERY (DO₂):
DO₂ = CO × CaO₂
CaO₂ = (Hb × 1.34 × SaO₂) + (PaO₂ × 0.003)

Normal DO₂ = 1000 mL/min
Normal VO₂ (consumption) = 250 mL/min
O₂ Extraction ratio = 25%

↓ DO₂ can occur from:
• ↓ CO (heart failure, shock)
• ↓ Hb (anaemia)
• ↓ SaO₂ (respiratory failure)

PAO₂ = (FiO₂ × 713) - (PaCO₂ / 0.8)

On room air (FiO₂ = 0.21, PaCO₂ = 40):
PAO₂ = (0.21 × 713) - (40/0.8)
     = 149.7 - 50 = ~100 mmHg

A-a GRADIENT = PAO₂ - PaO₂
Normal A-a gradient = <15 mmHg (on room air)

↑ A-a gradient = abnormality in lung (V/Q mismatch, diffusion problem, shunt)
Normal A-a gradient = problem is OUTSIDE the lung (hypoventilation, e.g. CNS)

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1E. Hypoxia — 4 Types (Exam Formula)

TYPE 1 — HYPOXIC HYPOXIA (↓ PaO₂):
Not enough O₂ getting into blood
Causes: COPD, pneumonia, PE, high altitude
↑ A-a gradient (V/Q mismatch) OR normal (pure hypoventilation)

TYPE 2 — ANAEMIC HYPOXIA (↓ Hb):
Not enough haemoglobin to carry O₂
PaO₂ NORMAL! SaO₂ NORMAL!
Causes: Anaemia, carbon monoxide poisoning (COHb)
CO Poisoning: PaO₂ looks normal but O₂ carrying capacity nil

TYPE 3 — STAGNANT/ISCHAEMIC HYPOXIA (↓ Blood flow):
Not enough blood reaching tissues
O₂ content normal, delivery ↓
Causes: Heart failure, shock, arterial obstruction

TYPE 4 — HISTOTOXIC HYPOXIA:
Cells cannot USE O₂ even though it's delivered
Cause: Cyanide poisoning, sepsis (mitochondrial dysfunction)
PaO₂ NORMAL, SvO₂ HIGH (cells reject O₂)

Hypoxic · Anaemic · Stagnant · Histotoxic

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1F. Respiratory Failure — Type 1 vs Type 2

TYPE 1 RESPIRATORY FAILURE:       TYPE 2 RESPIRATORY FAILURE:
PaO₂ < 60 mmHg                    PaO₂ < 60 mmHg
PaCO₂ NORMAL or LOW               PaCO₂ > 50 mmHg (CO₂ retention)
                                   
PROBLEM: OXYGENATION ONLY          PROBLEM: VENTILATION FAILURE
(Lungs getting O₂ in but           (Can't blow CO₂ out)
 something blocks it)
                                   
CAUSES:                            CAUSES:
• Pneumonia                        • COPD (severe)
• Pulmonary oedema                 • Chest wall deformity
• PE                               • Neuromuscular disease
• Fibrosis                         • Obesity hypoventilation
• ARDS                             • Drug overdose (opiates)
                                   • Acute severe asthma
MECHANISM: V/Q mismatch            MECHANISM: ↓ Alveolar ventilation
+ shunt                            → CO₂ builds up
                                   
TREAT: O₂ therapy                 TREAT: NIV (BiPAP) or
(Target 94–98%)                    intubation
                                   O₂ with CAUTION
                                   (target 88–92%)

In chronic COPD with CO₂ retention, the hypoxic drive replaces the normal CO₂ drive. Giving too much O₂ removes the drive to breathe → CO₂ rises further → respiratory arrest. TARGET SpO₂ = 88-92% only.

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1G. Control of Breathing

BREATHING CONTROL CENTRES (in brainstem):
┌─────────────────────────────────────────────────────┐
│ Medulla: Dorsal Respiratory Group (DRG) — INSPIRATION│
│           Ventral Respiratory Group (VRG) — EXPIRATION│
│ Pons: Pneumotaxic centre (limits inspiration)        │
│       Apneustic centre (prolongs inspiration)        │
└─────────────────────────────────────────────────────┘

CHEMICAL CONTROL:
PRIMARY DRIVER = PaCO₂
• Central chemoreceptors (medulla) → detect pH of CSF
• ↑ PaCO₂ → ↑ H+ in CSF → stimulates breathing
• This is the MAIN driver in normal people

SECONDARY DRIVER = PaO₂ (hypoxic drive)
• Peripheral chemoreceptors (carotid + aortic bodies)
• Only activated when PaO₂ <60 mmHg
• This is the driver in severe COPD (hypoxic drive)

MECHANICAL CONTROL:
• Hering-Breuer reflex: lung stretch receptors
  → when lung fully inflated → stops further inspiration
  → prevents over-inflation
• Irritant receptors → cough reflex
• J-receptors (juxtacapillary) → sense interstitial oedema
  → causes rapid shallow breathing (tachypnoea)
  → activated in pulmonary oedema, fibrosis, PE

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1H. Pathophysiology of ARDS (Acute Respiratory Distress Syndrome)

TRIGGER (direct or indirect lung injury):
Direct: Pneumonia, aspiration, inhalation injury
Indirect: Sepsis, pancreatitis, massive transfusion, trauma

PHASE 1 — EXUDATIVE (0–7 days):
Massive inflammatory cascade
↑ Neutrophil infiltration into alveoli
↑ Capillary permeability → Protein-rich fluid floods alveoli
Type II pneumocytes damaged → ↓ Surfactant production
→ Alveolar collapse (atelectasis)
→ Non-cardiogenic pulmonary oedema
→ Bilateral white-out on CXR ("white lung")
→ PaO₂/FiO₂ ratio <300 (mild), <200 (moderate), <100 (severe)

PHASE 2 — PROLIFERATIVE (7–21 days):
Type II pneumocyte proliferation (repair attempt)
Fibroblast activation → early fibrosis begins

PHASE 3 — FIBROTIC (>21 days):
Dense fibrosis if unresolved
→ Permanent restrictive defect
→ Pulmonary hypertension

BERLIN CRITERIA:
PaO₂/FiO₂ <300 = ARDS (onset within 1 week of insult)
<200 = Moderate ARDS
<100 = Severe ARDS
CXR: Bilateral opacities not explained by effusion/collapse/nodules
Not explained by cardiac failure (PCWP <18 or no hydrostatic oedema)

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╔══════════════════════════════════════╗

║ SECTION B: CARDIOVASCULAR SYSTEM ║

╚══════════════════════════════════════╝

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❤️ UNIT 2 — THE BASICS: HOW THE HEART WORKS

Real-World Analogy First

The heart is a pump with two sides working in series. The RIGHT side is a low-pressure primer pump sending blood to the lungs. The LEFT side is a high-pressure power pump pushing blood to the whole body. Both must match output perfectly — like two pumps in a pipeline.

---

2A. The Cardiac Cycle — Step by Step

DIASTOLE (heart RELAXES — filling phase):
Atria fill with blood from veins
AV valves open (mitral + tricuspid)
Ventricles fill passively → active atrial kick (last 20%)
End of diastole = MAXIMUM volume = EDV (End-Diastolic Volume)
Normal LV EDV = ~120–130 mL

SYSTOLE (heart CONTRACTS — ejection phase):
AV valves CLOSE (→ S1 heart sound: "LUB")
Isovolumetric contraction:
  Both sets of valves closed
  Pressure ↑ rapidly, volume unchanged
Semilunar valves OPEN (aortic + pulmonary)
  when LV pressure > Aortic pressure
Rapid ejection → Reduced ejection
Semilunar valves CLOSE (→ S2 heart sound: "DUB")
  when LV pressure falls below aortic pressure

End of systole = MINIMUM volume = ESV (End-Systolic Volume)
Normal LV ESV = ~50–60 mL

STROKE VOLUME (SV) = EDV - ESV = 70 mL (normal)

EJECTION FRACTION (EF) = SV / EDV × 100
Normal EF = 60–70%
EF <40% = systolic heart failure (HFrEF)

"LUB" (S1) = AV valves close = START of systole "DUB" (S2) = Semilunar valves close = END of systole S3 gallop = rapid ventricular filling — normal in young; abnormal in HF = "Kentucky" (lub-dub-ta) S4 gallop = stiff ventricle/atrial kick against resistance = HTN, HCM = "Tennessee" (ta-lub-dub)

---

2B. The 4 Determinants of Cardiac Output

CARDIAC OUTPUT (CO) = Stroke Volume (SV) × Heart Rate (HR)
Normal CO = 70 mL × 70 bpm = ~5 L/min

CO is determined by 4 factors:

1. PRELOAD                2. AFTERLOAD
   (filling volume)          (resistance to ejection)
   ↑Preload → ↑SV            ↑Afterload → ↓SV
   ↓Preload → ↓SV            ↓Afterload → ↑SV

3. CONTRACTILITY          4. HEART RATE
   (intrinsic muscle         ↑HR → ↑CO (up to ~150-180 bpm)
    strength)                Very ↑HR → ↓CO (too fast = no filling)
   ↑Contractility → ↑SV
   ↓Contractility → ↓SV

PRELOAD = filling pressure = EDV = venous return
AFTERLOAD = resistance against ejection = SVR = aortic pressure
CONTRACTILITY = independent of preload/afterload (inotropic state)

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2C. Frank-Starling Law — The Heart's Built-In Governor

The MORE the heart is stretched before contraction (more filling = more preload), the MORE FORCEFULLY it contracts and the MORE blood it ejects. Like a rubber band — the more you stretch it, the more it snaps back.

WHY DOES IT WORK?
At the cellular level (sarcomere):
• Optimal sarcomere length = 2.0–2.3 µm
  → Maximum actin-myosin cross-bridge overlap
  → Maximum force generated
• Below 2.0µm: too compressed — poor overlap — weak contraction
• Above 2.3µm: stretched too far — less overlap — weaker contraction
  (This is what happens in advanced heart failure — overstretched)

CLINICAL RELEVANCE:
IV fluids in dehydrated patient → ↑ venous return
→ ↑ EDV → ↑ sarcomere stretch → ↑ SV → ↑ CO  ✓

In heart failure (overstretched ventricle):
Giving too much fluid → ventricle on FLAT part of curve
→ No benefit, just congestion!

NORMAL heart:  More filling → More output (on steep part of curve)
FAILING heart: More filling → Same or LESS output (flat/descending curve)
               + Pulmonary oedema from backed-up pressure

---

2D. Blood Pressure Regulation — The Master System

MEAN ARTERIAL PRESSURE (MAP):
MAP = CO × SVR  (systemic vascular resistance)
MAP = DBP + 1/3(PP)  where PP = pulse pressure = SBP - DBP
Normal MAP = 70–100 mmHg

FORMULA: If MAP falls →
1. FAST RESPONSE (seconds): BARORECEPTORS
   ↓MAP detected at carotid sinus + aortic arch
   → ↓ stretch → ↓ afferent firing to vasomotor centre
   → ↑ Sympathetic outflow → ↑ HR + ↑ vasoconstriction → ↑ MAP
   (This is why you don't faint when you stand up suddenly — normally!)

2. INTERMEDIATE RESPONSE (minutes–hours): RAAS
   ↓MAP → ↓ renal perfusion
   → Renin released (juxtaglomerular cells)
   → Angiotensinogen → Angiotensin I → (ACE) → Angiotensin II
   → Vasoconstriction + ↑ Aldosterone
   → Na+ + H₂O retention → ↑ Blood volume → ↑ MAP

3. LONG-TERM RESPONSE (days–weeks): RENAL PRESSURE NATRIURESIS
   Kidney adjusts Na+/water excretion to set long-term BP
   This is why kidney disease → chronic hypertension

SYMPATHETIC SYSTEM ON THE HEART:
• β1 receptors → ↑ HR (chronotropy) + ↑ contractility (inotropy)
• α1 receptors in vessels → vasoconstriction

PARASYMPATHETIC SYSTEM ON THE HEART:
• Vagus nerve → ↓ HR only (slows SA node)
• No direct effect on ventricles

BP = CO × SVR
CO = HR × SV
SV = determined by Preload + Afterload + Contractility

So:
BP = HR × SV × SVR

Attack any component to lower BP:
• ↓HR: Beta-blockers
• ↓SV (↓preload): Diuretics, nitrates
• ↓SVR (↓afterload): ACEi, ARB, CCB, alpha-blockers
• ↓Contractility: Beta-blockers

---

2E. The Cardiac Conduction System

SA NODE (Sinoatrial node — right atrium):
"The Pacemaker"
• Intrinsic rate: 60–100 bpm
• Automaticity: spontaneous phase 4 depolarisation
  (pacemaker potential — "funny current" If)
• Controlled by ANS: Sympathetic ↑ rate; Parasympathetic ↓ rate

Signal travels:
SA Node → Atria (P wave on ECG)
        → AV Node (PR interval: 0.12–0.20s — DELAY here!)
        → Bundle of His
        → Left + Right Bundle Branches
        → Purkinje Fibres
        → Ventricular myocardium (QRS complex: <0.12s)
        → Ventricular REPOLARISATION (T wave)

WHY IS THERE A DELAY AT AV NODE?
→ Gives atria time to contract first and fill ventricles
  (the "atrial kick" = last 20% of ventricular filling)

BACKUP PACEMAKERS (fail-safes):
AV Node: 40–60 bpm (if SA fails)
Purkinje fibres: 20–40 bpm (if AV fails — very slow, unreliable)
Ventricular escape: <20 bpm

SA NODE (pacemaker cell):          VENTRICULAR MYOCYTE:
• Phase 4: Slow spontaneous        • Phase 4: FLAT (resting at -90mV)
  depolarisation (If current)      • Phase 0: Fast Na+ in (rapid rise)
• No true resting potential        • Phase 1: Brief repolarisation
• Phase 0: L-type Ca²+ in         • Phase 2: PLATEAU (Ca²+ in,
  (slow upstroke)                    K+ out balanced)
• No phase 1 or 2                  • Phase 3: Rapid K+ out
• Phase 3: K+ out                  • Refractory period prevents
                                     re-entry during plateau

KEY DRUG TARGETS:
β-blockers: ↓ Phase 4 slope in SA node → ↓ HR
Ca²+ blockers: ↓ Phase 0 in SA node → ↓ HR + ↓ conduction
Digoxin: ↑ Vagal tone → ↓ HR + ↑ contractility

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2F. Pathophysiology of Hypertension

BLOOD PRESSURE:
Normal: <120/80
Elevated: 120–129/<80
Stage 1 HTN: 130–139/80–89
Stage 2 HTN: ≥140/≥90
Crisis: >180/120

ESSENTIAL HTN (PRIMARY — 95%):
No single cause identified
MECHANISM:
Genetic + environmental → ↑ sympathetic activity
                       + ↑ RAAS activity
                       + Defective renal Na+ handling
                       ↓
                    ↑ SVR (vessel wall thickening)
                    + ↑ Blood volume
                       ↓
                    SUSTAINED ↑ BP

SECONDARY HTN (5%):
Cause identifiable — treat the cause!
• Renal: Renovascular disease (renal artery stenosis) — most common
  → ↓ Renal perfusion → ↑↑ Renin → ↑ Ang II → ↑↑ BP
• Endocrine: Conn's syndrome (↑Aldosterone) → Na+/H₂O retention
             Cushing's (↑Cortisol) → Na+ retention + ↑ SVR
             Phaeochromocytoma (↑Adrenaline) → ↑ HR + ↑ SVR
• Thyroid: Hyperthyroidism → ↑ CO + ↑ HR
• Coarctation of aorta: Upper body HTN + Radio-femoral delay

ORGAN DAMAGE FROM CHRONIC HTN:
Heart: LV Hypertrophy → Diastolic HF → Systolic HF
       → Coronary artery disease
Brain: Lacunar infarcts, cerebral haemorrhage,
       hypertensive encephalopathy
Kidney: Hyaline arteriolosclerosis → Chronic Kidney Disease
        (nephrosclerosis)
Eyes: Hypertensive retinopathy (AV nipping → flame haemorrhages
      → papilloedema in malignant HTN)
Vessels: Accelerated atherosclerosis → aortic aneurysm

---

2G. Pathophysiology of Heart Failure — Complete Story

FUNDAMENTAL CONCEPT:
Heart Failure = Cardiac output INSUFFICIENT to meet body's needs
OR adequate CO only at the expense of ↑ filling pressures

CAUSES:
SYSTOLIC FAILURE (HFrEF, EF <40%):
Can't PUMP (↓ contractility)
• MI/IHD (most common)
• Dilated cardiomyopathy
• Myocarditis
• Alcohol

DIASTOLIC FAILURE (HFpEF, EF ≥50%):
Can't RELAX (↑ stiffness)
• Hypertension (most common)
• HCM
• Restrictive CMP
• Amyloid

COMPENSATORY MECHANISMS AND WHY THEY FAIL:

COMPENSATION 1: FRANK-STARLING
↓CO → ↑ venous pressure → ↑ EDV → ↑ SV (Starling)
Initially helpful
FAILS when: Heart so overstretched it's on flat curve
             → Oedema builds up without benefit

COMPENSATION 2: SYMPATHETIC ACTIVATION
↓CO → Baroreceptors reset → ↑ SNS
→ ↑HR (tachycardia) + ↑ contractility + vasoconstriction
Initially: Maintains BP and CO
FAILS when:
• Tachycardia → ↓ diastolic filling time → ↓ SV
• Vasoconstriction → ↑ afterload → ↓ SV (vicious cycle!)
• Chronic catecholamines → cardiomyocyte DEATH (apoptosis)
• β1-receptor DOWNREGULATION → heart becomes unresponsive

COMPENSATION 3: RAAS ACTIVATION
↓ Renal perfusion → ↑ Renin → ↑ Angiotensin II → ↑ Aldosterone
→ Na+/water retention → ↑ blood volume → ↑ preload
Initially: Helps Starling mechanism
FAILS when:
• ↑↑ Volume → pulmonary oedema
• Ang II → promotes myocardial FIBROSIS (remodelling)
• Aldosterone → cardiac fibrosis + arrhythmias

COMPENSATION 4: CARDIAC REMODELLING
Hypertrophy + dilation of heart
Initially: Maintains wall stress (Laplace: stress = P×r / 2h)
FAILS when:
• Hypertrophied myocytes outgrow their blood supply → ischaemia
• Fibrosis replaces dead myocytes → ↓ contractility
• Dilation → dilates AV valve annulus → regurgitation → MORE volume load
• Fetal gene programme re-expressed → abnormal, less efficient proteins
• All of the above → progressive deterioration

THE VICIOUS CYCLE:
↓CO → Compensation → ↑ Afterload + ↑ Remodelling → ↓CO further
     ↓
Each compensatory mechanism contains the seeds of its own failure
     ↓
THIS IS WHY WE BLOCK THEM WITH DRUGS:
Beta-blockers → block SNS
ACEi/ARB → block RAAS
MRA (Spironolactone) → block Aldosterone
These are not just symptom drugs — they BREAK THE CYCLE

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2H. Coronary Circulation Physiology

CORONARY BLOOD FLOW:
Normal: 250 mL/min at rest (~5% of CO)
Maximum (exercise): up to 1250 mL/min (5× increase = coronary reserve)

KEY FACT: Coronary flow occurs mainly in DIASTOLE (not systole!)
Because: During systole → LV contraction squeezes coronary vessels shut
→ Blood can only flow in diastole (when myocardium relaxes)

IMPLICATION FOR TACHYCARDIA:
Very fast HR → ↓ diastolic time → ↓ coronary filling
→ This is why tachycardia WORSENS angina!
→ Beta-blockers lower HR → ↑ diastolic filling → ↑ coronary flow

CORONARY VASODILATION:
• Adenosine (metabolic — #1 local regulator)
• ↓ PaO₂ (local hypoxia → vasodilation — protective)
• Nitric oxide (endothelium-derived)
• Prostacyclin (PGI₂)

CORONARY VASOCONSTRICTION:
• Endothelin
• Thromboxane A₂ (from platelets)
• Serotonin
• Sympathetic α1 stimulation

MYOCARDIAL OXYGEN DEMAND determined by:
• Heart rate (rate-pressure product)
• Wall stress (afterload × radius / wall thickness — Laplace)
• Contractility

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2I. Pathophysiology of Shock — Universal Framework

SHOCK = Inadequate tissue perfusion → cellular hypoxia → organ failure

The ONE formula: MAP = CO × SVR

ALL SHOCK is a problem with MAP:
Either ↓ CO (pump or volume problem)
Or ↓ SVR (vessels too dilated — maldistribution)

4 TYPES OF SHOCK:

TYPE 1 — HYPOVOLAEMIC (↓ blood volume → ↓ CO):
Cause: Haemorrhage, burns, vomiting/diarrhoea, dehydration
Mechanism: ↓ Venous return → ↓ EDV → ↓ SV (Starling) → ↓ CO
Signs: Cool/clammy skin (↑ SVR compensation), ↓BP, ↑HR, ↓JVP
Treat: IV fluid replacement / Blood products

TYPE 2 — CARDIOGENIC (↓ pump function → ↓ CO):
Cause: MI, severe heart failure, arrhythmia, tamponade
Mechanism: ↓ Contractility → ↓ SV → ↓ CO
Signs: Cool/clammy, ↓BP, ↑HR, ↑JVP, pulmonary oedema
Treat: Inotropes (dobutamine), revascularisation, IABP

TYPE 3 — DISTRIBUTIVE (↓ SVR → maldistribution):
Cause: SEPSIS (#1), anaphylaxis, neurogenic
Mechanism: Vasodilation → blood pools in periphery
           → ↓ venous return → ↓ CO
           ALSO: in sepsis → ↓ contractility + ↑ permeability
Signs: WARM/vasodilated (early sepsis), ↓BP, ↑HR, ↑CO (paradox!)
       Late sepsis: cold, ↑ lactate, multi-organ failure
Treat: Fluids + vasopressors (noradrenaline) + antibiotics

TYPE 4 — OBSTRUCTIVE (physical block to blood flow):
Cause: PE, tension pneumothorax, cardiac tamponade
Mechanism: Physical obstruction of venous return or cardiac output
PE: emboli block pulmonary artery → ↑ RV afterload → ↓ LV filling → ↓ CO
Tension PTX: ↑ intrathoracic pressure → compresses great veins
Tamponade: fluid compresses cardiac chambers → ↓ filling
Signs: ↑JVP, ↓BP, ↑HR, specific features per cause
Treat: Remove the obstruction (drain, thrombolysis, needle decompression)

TYPE          CO      SVR     JVP      SKIN
─────────────────────────────────────────────────
Hypovolaemic  ↓↓      ↑       ↓       COLD/CLAMMY
Cardiogenic   ↓↓      ↑       ↑       COLD/CLAMMY
Distributive  ↑(early)↓↓      ↓       WARM/FLUSHED
Obstructive   ↓↓      ↑       ↑↑      COLD/CLAMMY

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2J. Pulmonary Hypertension — The Bridge Between Systems

DEFINITION: Mean PAP > 20 mmHg at rest (new criteria 2022)
Normal mPAP = 8–20 mmHg

WHO GROUPS:
Group 1 — PAH (Pulmonary Arterial Hypertension):
   Idiopathic, heritable (BMPR2 mutation), drugs (fenfluramine),
   connective tissue disease, HIV, portal HTN, congenital heart disease
   MECHANISM: ↑ Vasoconstriction + vascular remodelling (plexiform lesions)
              Endothelin ↑, NO ↓, Prostacyclin ↓

Group 2 — Left heart disease (MOST COMMON OVERALL):
   LV failure → backed-up pressure → ↑ Pulmonary venous pressure
   → Passive ↑ PAP ("reactive" PH)
   TREATMENT: Treat the left heart!

Group 3 — Lung disease / Hypoxia:
   COPD, fibrosis → chronic hypoxia
   → Hypoxic pulmonary vasoconstriction (HPV) — chronic → remodelling

Group 4 — Chronic thromboembolic (CTEPH):
   Unresolved PE → fibrotic occlusion → ↑ RV afterload
   TREATMENT: Pulmonary endarterectomy (surgical — curable!)

Group 5 — Miscellaneous: Sarcoidosis, haematological

CONSEQUENCES:
↑ PAP → ↑ RV Afterload → RV Hypertrophy → RV Failure
= COR PULMONALE
Symptoms: Progressive dyspnoea, right heart failure signs
          (JVD, peripheral oedema, hepatomegaly)

TREATMENT (Group 1 — PAH):
• Calcium channel blockers (only vasoreactive patients)
• Endothelin antagonists (Bosentan, Macitentan)
• PDE5 inhibitors (Sildenafil, Tadalafil) — ↑ cGMP/NO
• Prostacyclin analogues (Epoprostenol IV, Iloprost inhaled)
• Riociguat (soluble guanylate cyclase stimulator)
• Lung/heart-lung transplantation (end-stage)

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═══════════════════════════════════

MASTER INTEGRATION MAP

How Respiratory & Cardiovascular Systems Cross-Talk

═══════════════════════════════════

                RESPIRATORY FAILURE
                        ↓
            ↓ PaO₂ / ↑ PaCO₂
                        ↓
    ┌───────────────────┴───────────────────┐
    ▼                                       ▼
HYPOXIC PULMONARY              SYMPATHETIC ACTIVATION
VASOCONSTRICTION                  ↑ HR + ↑ SVR
(protective short-term)           ↑ Cardiac work
    ↓ (if chronic)                ↓ (if severe)
PULMONARY HYPERTENSION         MYOCARDIAL ISCHAEMIA
    ↓                           (O₂ demand > supply)
RV HYPERTROPHY                      ↓
    ↓                          CARDIOGENIC SHOCK
COR PULMONALE                       ↓
(Right Heart Failure)         PULMONARY OEDEMA
    ↓                               ↓
PERIPHERAL OEDEMA              WORSENING HYPOXIA
JVD, hepatomegaly                   ↓
                             MORE RESPIRATORY FAILURE
                        ← VICIOUS CYCLE →

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ONE-PAGE FORMULA BANK (Revise 5 min before exam)

RESPIRATORY:
TLC = TV + IRV + ERV + RV             (~6L)
VC  = TV + IRV + ERV                  (~4.8L)
FRC = ERV + RV                        (~2.5L)
Normal V/Q = 0.8
PAO₂ = (FiO₂ × 713) - (PaCO₂/0.8)   (alveolar gas equation)
A-a gradient = PAO₂ - PaO₂            (normal <15mmHg)
Compliance = ΔV/ΔP                    (normal 0.2 L/cmH₂O)

CARDIOVASCULAR:
CO = SV × HR                          (~5 L/min)
SV = EDV - ESV                        (~70 mL)
EF = SV/EDV × 100                     (normal 60-70%)
MAP = CO × SVR                        (normal 70–100 mmHg)
MAP = DBP + 1/3(SBP - DBP)
TPR = (MAP - CVP) / CO
DO₂ = CO × CaO₂                      (normal ~1000 mL/min)
CaO₂ = (Hb × 1.34 × SaO₂) + (PaO₂ × 0.003)
Laplace: Wall stress = P × r / 2h    (explains hypertrophy benefit)

TYPE 1 RF: ↓PaO₂, normal/↓PaCO₂ = oxygenation failure
TYPE 2 RF: ↓PaO₂, ↑PaCO₂ = ventilation failure
HFrEF: EF <40% = can't squeeze
HFpEF: EF ≥50% = can't relax
Shock = MAP = CO × SVR (find what's low, fix it)

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🔥 PATHOPHYSIOLOGY — DISEASE BY DISEASE

CVS + RESPIRATORY | Medicine × Pathology COMBO

Super Easy · Super Smart · Super Real

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THE GOLDEN THREAD for every disease: Cause → Mechanism → Structural Change (Pathology) → Clinical Features (Medicine) → Complications Master this thread and you own every question.

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╔══════════════════════════════╗

║ CARDIOVASCULAR DISEASES ║

╚══════════════════════════════╝

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🔴 1. HYPERTENSION

CAUSE
└── Essential (95%): Genetic + Lifestyle (↑ salt, obesity, smoking)
    Secondary (5%): Renal artery stenosis, Conn's, Phaeochromocytoma
         ↓
MECHANISM
└── ↑ SVR (vessel wall thickening) + ↑ Blood volume (RAAS)
    Angiotensin II → vasoconstriction + aldosterone → Na/H₂O retention
         ↓
STRUCTURAL CHANGE (PATHOLOGY)
┌─────────────────────────────────────────────────────┐
│ HEART: LV concentric hypertrophy                    │
│  (pressure overload → sarcomeres parallel → thick   │
│   wall → STIFF ventricle = diastolic dysfunction)   │
│                                                     │
│ VESSELS:                                            │
│  Hyaline arteriolosclerosis (benign HTN)            │
│  Hyperplastic arteriolosclerosis (malignant HTN)    │
│  = "Onion-skin" concentric wall thickening          │
│  Fibrinoid necrosis in severe hypertensive crisis   │
│  Accelerated atherosclerosis in large vessels       │
│                                                     │
│ KIDNEY: Hyaline thickening of afferent arterioles   │
│  → Ischaemic glomerular damage (nephrosclerosis)    │
│  → Chronic Kidney Disease                           │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)
• Usually ASYMPTOMATIC (silent killer!)
• Headache (occipital, morning) in severe
• Epistaxis, visual changes (blurred vision)
• Signs: ↑BP, loud A2, LV heave, S4 gallop
• Fundoscopy: AV nipping → flame haemorrhages
  → papilloedema (malignant HTN)
         ↓
COMPLICATIONS
Heart: LVH → Diastolic HF → Systolic HF → IHD → Arrhythmia
Brain: Lacunar infarcts, Hypertensive encephalopathy, ICH
Kidney: CKD → ESRD
Vessels: Aortic aneurysm, Aortic dissection, PAD
Eyes: Hypertensive retinopathy → blindness

HTN → ↑ Pressure overload on LV → Concentric LVH (Pathology) → Diastolic dysfunction (Medicine) → LV fills poorly → Pulmonary congestion → Dyspnoea on exertion

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🔴 2. ISCHEMIC HEART DISEASE (IHD) — FULL STORY

CAUSE
└── Atherosclerosis (90%) → Coronary artery narrowing
    + Thrombosis on plaque rupture (acute events)
         ↓
MECHANISM
└── Coronary supply CANNOT meet myocardial demand
    Supply ↓: Stenosis, spasm, thrombosis
    Demand ↑: Exertion, tachycardia, hypertrophy
         ↓
STRUCTURAL CHANGE (PATHOLOGY) — TIME-BASED

REVERSIBLE ISCHAEMIA (no permanent damage):
• Myocyte fatty change (fat vacuoles accumulate)
• Cellular swelling (Na+ pump failure)
• No necrosis → ANGINA clinically

IRREVERSIBLE INJURY → INFARCTION:
0–6 hrs:   No H&E change! (Wavy fibres on EM only)
           Gross: normal / slightly pale
6–24 hrs:  Coagulative necrosis begins
           Gross: pale/mottled
Day 1–3:   NEUTROPHIL infiltration (peak)
           Gross: pale yellow, soft
Day 3–7:   MACROPHAGE infiltration (removing debris)
           Gross: YELLOW, SOFT — ⚠ RUPTURE RISK!
Week 1–3:  GRANULATION TISSUE (new vessels + fibroblasts)
           Gross: Red-grey rim
>6 weeks:  Dense COLLAGEN SCAR
           Gross: White, firm, shrunken
         ↓
CLINICAL FEATURES (MEDICINE)

STABLE ANGINA:
• Chest pain on exertion → relieved by rest/GTN
• ECG: ST depression during episode
• Troponin: NEGATIVE

UNSTABLE ANGINA / NSTEMI:
• Chest pain at rest or increasing severity
• Troponin: POSITIVE (NSTEMI)
• ECG: ST depression + T wave changes

STEMI:
• Severe crushing chest pain > 20 minutes
• ECG: ST ELEVATION + new Q waves later
• Troponin: STRONGLY POSITIVE
• Radiation: Left arm, jaw, shoulder, back
• Autonomic: sweating, nausea, vomiting
         ↓
COMPLICATIONS
Immediate: VF (50% die before hospital — arrhythmia #1 killer)
Day 1-3:   Cardiogenic shock (>40% LV lost)
Day 3-7:   Free wall rupture → tamponade
           Papillary muscle rupture → acute MR
           Septal rupture → VSD
Weeks:     Dressler syndrome, mural thrombus
Months:    Ventricular aneurysm, chronic HF

Atherosclerotic plaque rupture → Thrombus → Coronary occlusion → Ischaemia → Coagulative necrosis (Pathology: neutrophils day 1-3, macrophages day 3-7, scar >6wks) → Clinically: Chest pain + ST elevation + ↑ Troponin (Medicine) → If untreated → Cardiogenic shock + VF

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🔴 3. CONGESTIVE CARDIAC FAILURE (CCF) — COMPLETE PICTURE

CAUSE
└── IHD (#1), HTN, Valvular disease, Cardiomyopathy,
    Myocarditis, Arrhythmia, Congenital
         ↓
MECHANISM (The 3-Layer Story)
LAYER 1 — INITIAL HIT:
• Lost/damaged myocardium (MI)
• Pressure overload (HTN, AS) → can't relax
• Volume overload (MR, AR) → can't empty
         ↓
LAYER 2 — COMPENSATION:
┌────────────────────────────────────────────────┐
│ Frank-Starling:   ↑Filling → ↑Output           │
│ Sympathetic:      ↑HR + ↑Contractility         │
│ RAAS:             Na/H₂O retention             │
│ Hypertrophy:      ↑Wall thickness              │
└────────────────────────────────────────────────┘
         ↓
LAYER 3 — DECOMPENSATION (compensation fails):
Frank-Starling → Ventricle overstretched → Oedema
SNS → Vasoconstriction → ↑ Afterload → ↓ SV further
RAAS → Fluid overload → Pulmonary oedema
Hypertrophy → Fibrosis → Arrhythmias → ↓ EF
         ↓
STRUCTURAL CHANGE (PATHOLOGY)
┌─────────────────────────────────────────────────────┐
│ HEART:                                              │
│  Hypertrophy + Dilation (eccentric or concentric)  │
│  Interstitial FIBROSIS (collagen replaces myocytes) │
│  Myocyte disorganisation, vacuolation               │
│  LA dilation → AF → thrombus in LA appendage       │
│                                                     │
│ LUNGS (Left HF):                                    │
│  Heavy, wet, boggy lungs                            │
│  Interstitial + alveolar oedema                     │
│  HEART FAILURE CELLS (haemosiderin-laden           │
│  macrophages) — pathognomonic of chronic LHF        │
│  Haemosiderin from RBC breakdown in alveoli         │
│                                                     │
│ LIVER (Right HF):                                   │
│  NUTMEG LIVER (passive congestion)                  │
│  Centrizonal necrosis → cardiac cirrhosis (chronic) │
│                                                     │
│ KIDNEYS: Prerenal azotaemia                         │
│ SPLEEN: Passive congestion → splenomegaly           │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)

LEFT HEART FAILURE:            RIGHT HEART FAILURE:
Dyspnoea on exertion           Peripheral pitting oedema
Orthopnoea (2+ pillows)        ↑ JVP (raised neck veins)
PND (woken at night)           Hepatomegaly (tender)
Cough (pink frothy sputum)     Ascites
Fine basal crackles            Anorexia/nausea
S3 gallop                      Pleural effusion (bilateral)

INVESTIGATIONS:
• CXR: Cardiomegaly (CTR >0.5) + pulmonary oedema
  "ABCDE" on CXR:
  A = Alveolar oedema (bat-wing)
  B = Kerley B lines (interstitial oedema)
  C = Cardiomegaly
  D = Dilated upper lobe veins
  E = Effusion (pleural)
• Echo: ↓ EF (<40% = HFrEF), dilated chambers
• BNP/NT-proBNP: ↑↑ (biomarker of wall stress)
• ECG: LVH, LBBB, AF

↓ CO → Compensation fails → Blood backs up: Left → Pulmonary congestion → Heavy wet lungs + HF cells (Pathology) → Dyspnoea + crackles (Medicine) Right → Systemic congestion → Nutmeg liver + pitting oedema (both)

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🔴 4. RHEUMATIC FEVER + RHEUMATIC HEART DISEASE

CAUSE
└── Group A Streptococcal pharyngitis
    → 2-3 week latent period
         ↓
MECHANISM (Molecular Mimicry)
└── Anti-Strep antibodies (vs M protein)
    CROSS-REACT with cardiac proteins
    → Immune-mediated cardiac injury
    (Strep NOT present in lesions!)
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

ACUTE RHEUMATIC FEVER:
┌─────────────────────────────────────────────────────┐
│ ASCHOFF BODIES (pathognomonic):                     │
│  Central fibrinoid necrosis                         │
│  + Anitschkow cells ("caterpillar cells")           │
│    (macrophages with wavy chromatin)                │
│  + Langhans giant cells + lymphocytes               │
│  Found in ALL 3 layers of heart = PANCARDITIS       │
│                                                     │
│ ENDOCARDITIS:                                       │
│  Small VERRUCAE (1-2mm) along valve CLOSURE LINE   │
│  (Mitral > Aortic > Tricuspid > Pulmonary)          │
│                                                     │
│ PERICARDITIS: "Bread and butter" fibrinous          │
└─────────────────────────────────────────────────────┘

CHRONIC RHD (after repeated attacks):
┌─────────────────────────────────────────────────────┐
│ MITRAL STENOSIS (virtually only cause = RHD):       │
│  Leaflet thickening + commissural FUSION            │
│  Chordae tendineae thickening + fusion              │
│  "Fish-mouth" or "button-hole" orifice              │
│  Calcification of valve leaflets                    │
│  Neovascularisation of valve (chronic inflammation) │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE) — Jones Criteria

MAJOR:         MINOR:
Carditis        Fever
Arthritis       ↑ ESR/CRP
Chorea          Prolonged PR interval
Erythema marginatum
Subcutaneous nodules

MITRAL STENOSIS SIGNS:
• Malar flush (butterfly-shaped facial redness)
• Opening snap + mid-diastolic rumble (apex)
• Loud S1
• AF → ↑ risk of LA thrombus → emboli → STROKE
         ↓
PROGRESSION CHAIN
Repeated RF → Mitral stenosis → LA enlargement
→ AF → Systemic emboli + Pulmonary HTN
→ RV hypertrophy → Right heart failure

Strep throat → Molecular mimicry → Aschoff bodies + Verrucae (Pathology) → Pancarditis (Jones criteria: carditis, arthritis, chorea) (Medicine) → Repeated episodes → Fish-mouth mitral stenosis → AF + Pulmonary HTN

---

🔴 5. ATHEROSCLEROSIS + ATHEROMA

CAUSE
└── Risk factors: HTN, DM, Smoking, Dyslipidaemia,
    Obesity, Family history, Male sex, Age
         ↓
MECHANISM — 5 STEPS

STEP 1: ENDOTHELIAL INJURY
↑ Shear stress (HTN) + Oxidised LDL + Smoking toxins
→ Endothelial dysfunction

STEP 2: LDL ENTRY + OXIDATION
Increased permeability → LDL enters intima
→ Oxidised by reactive oxygen species (ROS)

STEP 3: MONOCYTE RECRUITMENT
Endothelium expresses ICAM-1, VCAM-1
→ Monocytes adhere → Migrate into intima
→ Differentiate into MACROPHAGES

STEP 4: FOAM CELL FORMATION
Macrophages engulf oxidised LDL via scavenger receptors
→ Lipid-laden FOAM CELLS accumulate
→ FATTY STREAK (earliest visible lesion — reversible!)

STEP 5: PLAQUE FORMATION
SMCs migrate from media → intima
SMCs proliferate + secrete ECM (collagen, proteoglycans)
Lipid core (cholesterol + debris) accumulates
Fibrous cap forms over lipid core
→ FIBROUS PLAQUE
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

STABLE PLAQUE:               VULNERABLE PLAQUE:
Thick fibrous cap             Thin fibrous cap
Heavy calcification           Large lipid core
Few macrophages               Many macrophages
Gradual lumen stenosis        Shoulder region inflamed
→ Stable angina               → Plaque rupture!
                              → Thrombosis → MI / Stroke

COMPLICATED PLAQUE (advanced):
Calcification · Ulceration · Haemorrhage into plaque
Surface thrombosis · Aneurysm formation
         ↓
CLINICAL FEATURES (MEDICINE)
• Coronary → Angina → MI → Sudden death
• Cerebral → TIA → Stroke
• Peripheral → Claudication → Rest pain → Gangrene
• Renal artery → Renovascular HTN → CKD
• Aorta → Aneurysm → Rupture

Plaque RUPTURE (not stenosis) causes MI Plaque EROSION → also causes thrombosis (especially in young women/diabetics) Stable plaque = symptoms from stenosis only

---

╔══════════════════════════════╗

║ RESPIRATORY DISEASES ║

╚══════════════════════════════╝

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🟢 6. ASTHMA

CAUSE
└── Atopic (IgE-mediated): Allergens — dust mite, pollen, animal
    Non-atopic: Cold air, exercise, aspirin, infection, stress
         ↓
MECHANISM — 2-PHASE RESPONSE

PHASE 1 — EARLY (minutes):
Allergen → IgE on Mast cells → DEGRANULATION
Histamine → Bronchospasm + Mucosal oedema
Leukotrienes (LTC4/D4/E4) → Prolonged bronchospasm + Mucus

PHASE 2 — LATE (6-12 hours):
Eosinophils recruited (via IL-5)
Major Basic Protein (MBP) → Epithelial DAMAGE
Th2 cells → IL-4, IL-13 → Goblet cell hyperplasia
→ ↑↑ Mucus production
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

ACUTE:                        CHRONIC (REMODELLING):
Bronchospasm                  Basement membrane THICKENING
Mucosal oedema                Subepithelial FIBROSIS
Mucus hypersecretion          Smooth muscle HYPERTROPHY
Mucus plugs                   Goblet cell HYPERPLASIA
(Curschmann spirals)          Eosinophil infiltration
Eosinophil infiltrate         → Permanent (irreversible) changes
Charcot-Leyden crystals
(eosinophil breakdown)
         ↓
CLINICAL FEATURES (MEDICINE)

TRIAD: Wheeze + Cough + Dyspnoea (episodic, variable)
• REVERSIBLE airflow obstruction
• Wheeze (expiratory) — air squeezed through narrow tubes
• Prolonged expiration (air trapped, can't get out)
• Hyperinflated chest (barrel chest in severe/chronic)
• "Silent chest" in life-threatening = no air moving at all

SPIROMETRY: FEV1/FVC <0.70 + ≥12% reversibility with BD
CXR: Usually normal OR hyperinflation
ABG early: ↑pH, ↓CO₂ (hyperventilating)
ABG late: ↓pH, ↑CO₂ (tiring — DANGER SIGN!)
Sputum: Eosinophils + Curschmann spirals + Charcot-Leyden crystals

Allergen → Mast cell → Histamine + Leukotrienes → Bronchospasm + mucosal oedema (Pathology) → Wheeze + Dyspnoea (Medicine) → Chronic → Subepithelial fibrosis + smooth muscle hypertrophy → Remodelling

---

🟢 7. COPD (Emphysema + Chronic Bronchitis)

CAUSE
└── Cigarette smoking (90%), Air pollution,
    α1-antitrypsin deficiency (rare, young onset)
         ↓
MECHANISM

SMOKING → Macrophage + Neutrophil activation
         ↓
     ┌───────────┴────────────────┐
     ▼                            ▼
ELASTASE/PROTEASE            MUCUS GLAND
↑ Elastase (from neutrophils)  STIMULATION
↓ α1-antitrypsin (inhibitor)   ↑ Goblet cells
→ Alveolar wall DESTRUCTION    ↑ Reid index
         ↓                           ↓
    EMPHYSEMA               CHRONIC BRONCHITIS
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

EMPHYSEMA:
┌─────────────────────────────────────────────────────┐
│ Permanent ENLARGEMENT of airspaces DISTAL to        │
│ terminal bronchiole + DESTRUCTION of alveolar walls │
│ WITHOUT fibrosis                                    │
│                                                     │
│ CENTRIACINAR (centrilobular):                       │
│  Respiratory bronchioles destroyed first            │
│  SMOKING-related (most common)                      │
│  UPPER lobe predominance                            │
│                                                     │
│ PANACINAR (panlobular):                             │
│  Entire acinus destroyed                            │
│  α1-ANTITRYPSIN DEFICIENCY                          │
│  LOWER lobe predominance                            │
│                                                     │
│ Gross: Large bullae visible                         │
│ Micro: Loss of alveolar walls, enlarged airspaces   │
└─────────────────────────────────────────────────────┘

CHRONIC BRONCHITIS:
┌─────────────────────────────────────────────────────┐
│ REID INDEX = Mucous gland thickness/Bronchial wall  │
│ Normal <0.4; Chronic bronchitis >0.5                │
│ Mucus gland hypertrophy + Goblet cell hyperplasia   │
│ Squamous metaplasia of bronchial epithelium         │
│ Chronic inflammation in bronchial wall              │
│ Luminal mucus plugging                              │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)

EMPHYSEMA ("Pink Puffer"):      CHRONIC BRONCHITIS ("Blue Bloater"):
Thin, barrel chest               Obese, cyanosed, oedematous
Severe dyspnoea                  Productive cough ≥3 months × 2yrs
Pursed-lip breathing             Recurrent chest infections
Near-normal PaO₂ (compensates)  ↓ PaO₂, ↑ PaCO₂ (CO₂ retainer)
Quiet chest on auscultation     Wheeze + coarse crackles

BOTH: FEV1/FVC <0.70 (irreversible obstruction)
      Hyperinflation on CXR
      FEV1 progressively falls (irreversible)

Smoking → ↑ Elastase vs ↓ α1-AT → Alveolar wall destruction (Emphysema pathology) → Air trapping → Barrel chest + Pursed lips (Medicine) + Mucus gland hypertrophy (Reid >0.5) → Productive cough → COPD

---

🟢 8. PNEUMONIA

CAUSE
└── Community: Strep pneumoniae (#1), Mycoplasma, Legionella
    Hospital: Pseudomonas, Klebsiella, Staph aureus
    Immunocompromised: PCP, Aspergillus
         ↓
MECHANISM
└── Organism reaches alveoli → Overwhelms defences
    → Local inflammation + exudate floods alveoli
    → Alveolar consolidation
         ↓
STRUCTURAL CHANGE (PATHOLOGY) — 4 STAGES

LOBAR PNEUMONIA STAGES:
┌─────────────────────────────────────────────────────┐
│ STAGE 1 — CONGESTION (Day 1-2):                    │
│  Vascular engorgement + Serous fluid in alveoli    │
│  Bacteria multiplying                              │
│  Lung: RED, heavy, boggy                           │
│                                                     │
│ STAGE 2 — RED HEPATISATION (Day 2-4):              │
│  Alveoli packed: RBCs + Fibrin + Neutrophils       │
│  Lung: SOLID, RED, liver-like texture              │
│  "Hepatisation" = like liver on cut section        │
│                                                     │
│ STAGE 3 — GREY HEPATISATION (Day 4-8):             │
│  RBCs lyse → Grey/green colour                     │
│  Fibrin + Macrophages dominate                     │
│  Bacteria being cleared                            │
│  Lung: GREY, firm                                  │
│                                                     │
│ STAGE 4 — RESOLUTION (Day 8-10):                   │
│  Macrophages digest fibrin enzymatically           │
│  Alveolar architecture PRESERVED                   │
│  Return to normal (if uncomplicated)               │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)

• Fever, rigors, productive cough
• Rusty sputum (Strep pneumoniae)
• Pleuritic chest pain (pleural involvement)
• Dyspnoea, tachycardia
• SIGNS: Dull on percussion, ↑ tactile fremitus/VF,
         Bronchial breathing (consolidated lung transmits sound),
         Aegophony, Crackles
• CXR: Lobar consolidation (white opacity)
       Air bronchogram (airways visible within opacity)
• Bloods: ↑ WBC (neutrophilia), ↑ CRP
• CURB-65 for severity scoring

Organism → Inflammatory exudate fills alveoli → 4 stages: Congestion → Red → Grey hepatisation → Resolution (Pathology) → Clinically: Consolidation = Dull percussion + Bronchial breathing + ↑ VF (Medicine) — all explained by alveolar consolidation

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🟢 9. TUBERCULOSIS

CAUSE
└── Mycobacterium tuberculosis (aerobic, acid-fast bacillus)
    Inhaled droplet nuclei <5 µm → reach alveoli
         ↓
MECHANISM

M. tuberculosis → Engulfed by Alveolar Macrophages
→ SURVIVES by inhibiting phagosome-lysosome fusion
→ Antigen presentation to CD4+ T cells
→ Th1 response → IFN-γ → Macrophage ACTIVATION
→ Epithelioid macrophages + Langhans Giant Cells
→ GRANULOMA FORMATION
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

PRIMARY TB:
┌─────────────────────────────────────────────────────┐
│ GHON FOCUS: Subpleural caseating granuloma          │
│  (usually lower-upper or upper-lower lobe junction) │
│  +                                                  │
│ Hilar lymph node involvement                        │
│  = GHON COMPLEX                                     │
│  ↓ Calcifies → RANKE COMPLEX (healed primary TB)   │
└─────────────────────────────────────────────────────┘

SECONDARY (POST-PRIMARY) TB (reactivation):
┌─────────────────────────────────────────────────────┐
│ UPPER LOBE apical + posterior segments              │
│ (high O₂ tension favours aerobic mycobacteria)      │
│                                                     │
│ CASEATING GRANULOMA:                                │
│  Epithelioid macrophages (activated)                │
│  Langhans Giant Cells (horseshoe nuclei)            │
│  Lymphocytes at periphery                           │
│  Central CASEATION (cheese-like necrosis)           │
│  = pathognomonic of TB                              │
│                                                     │
│ CAVITATION: Central caseum liquefies                │
│  → Bronchus drains it → CAVITY forms                │
│  Cavity wall = fibrous + necrotic                   │
│                                                     │
│ MILIARY TB: 1-2mm millet-seed granulomas            │
│  throughout lungs + other organs (haematogenous)    │
└─────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)

PRIMARY TB: Usually SILENT (mild flu-like illness)
SECONDARY TB:
• Constitutional: Fever, Night sweats, Weight loss ("consumption")
• Respiratory: Cough (>3 weeks) → Haemoptysis (cavity erodes vessel)
• Signs: Dull apex, Bronchial breathing over cavity
• CXR: Apical/upper lobe infiltrates, cavitation, calcification
• Mantoux/IGRA: Positive
• Sputum AFB: Positive (3 morning samples)
• GeneXpert: Rapid TB + Rifampicin resistance detection

COMPLICATIONS:
• Massive haemoptysis (Rasmussen's aneurysm)
• Bronchogenic spread → new foci
• Miliary TB → meningitis, Pott's disease (spine), Addison's
• Respiratory failure
• Secondary amyloidosis (AA type, chronic inflammation)

---

🟢 10. PULMONARY EMBOLISM (PE)

CAUSE
└── DVT (proximal leg/pelvic veins → dislodges → travels to lung)
    Virchow's Triad: Stasis + Hypercoagulability + Endothelial injury
         ↓
MECHANISM
└── Embolus lodges in pulmonary artery
         ↓
    ┌──────────────────────────────────────┐
    │ MECHANICAL OBSTRUCTION:             │
    │ ↑ RV afterload → RV dilatation      │
    │ Interventricular septum bows LEFT   │
    │ → ↓ LV filling → ↓ CO → Shock      │
    │                                     │
    │ HUMORAL EFFECTS:                    │
    │ Serotonin + TXA2 → Vasoconstriction │
    │ → Further ↑ pulmonary resistance    │
    │                                     │
    │ V/Q MISMATCH:                       │
    │ Ventilated alveoli, no perfusion    │
    │ → Dead space → Hypoxia             │
    └──────────────────────────────────────┘
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

SMALL PE (end-artery):
• Pulmonary INFARCTION: Wedge-shaped, haemorrhagic
  Apex points to hilum (direction of obstructed vessel)
  Pleural surface involved → Fibrinous pleuritis
  → Haemorrhagic infarct turns brown/grey

MASSIVE PE:
• RV dilatation + hypertrophy (acute cor pulmonale)
• Saddle embolus at bifurcation of main PA
         ↓
CLINICAL FEATURES (MEDICINE)

CLASSIC TRIAD (only present together in 20%!):
① Dyspnoea (sudden onset)
② Pleuritic chest pain (if infarction)
③ Haemoptysis (if infarction)

Other features: Tachycardia, tachypnoea, ↓ BP (massive)
Signs of DVT: Calf pain, warmth, swelling
ECG: Sinus tachycardia (most common)
     S1Q3T3 (classic but rare)
     RBBB
ABG: ↓ PaO₂, ↓ PaCO₂ (hyperventilating), ↑ A-a gradient
D-dimer: Sensitive NOT specific (negative rules out PE)
CTPA: Gold standard investigation
Wells Score: Pre-test probability
Echo: RV dilatation, septal bowing = "D-sign"

DVT → Embolus → PA obstruction → ↑ RV afterload + V/Q mismatch (Mechanism) → Wedge-shaped haemorrhagic infarct (Pathology) → Sudden dyspnoea + pleuritic pain + hypoxia (Medicine) → Massive PE → RV failure + shock

---

🟢 11. LUNG CARCINOMA

CAUSE
└── Smoking (90%), Asbestos (mesothelioma + BrCa),
    Radon gas, Occupational carcinogens
    EGFR/KRAS/ALK mutations (Adenocarcinoma)
         ↓
MECHANISM
└── Carcinogens → DNA mutations (RAS, p53, RB genes)
    Normal epithelium → Hyperplasia → Metaplasia
    → Dysplasia → Carcinoma in situ → INVASION
         ↓
STRUCTURAL CHANGE (PATHOLOGY)

┌──────────────────────────────────────────────────────┐
│ SQUAMOUS CELL (30%):                                │
│  CENTRAL (main bronchi)                             │
│  Keratin pearls + Intercellular bridges on histo    │
│  Cavitation common (necrotic centre)                │
│  Strong smoking link                                │
│                                                     │
│ ADENOCARCINOMA (40% — most common overall):         │
│  PERIPHERAL (pleural surface)                       │
│  Glandular formation + Mucin production             │
│  TTF-1, CK7, Napsin A positive                      │
│  Non-smokers, women, younger patients               │
│  EGFR mutation (targetable → Gefitinib)             │
│                                                     │
│ SMALL CELL (15%):                                   │
│  CENTRAL (main bronchi)                             │
│  "Oat cells": small, dark, scant cytoplasm          │
│  Neuroendocrine origin (Kulchitsky cells)           │
│  NSE, chromogranin, synaptophysin positive          │
│  Very early metastasis → surgical cure RARE         │
│                                                     │
│ LARGE CELL (10%):                                   │
│  PERIPHERAL, poorly differentiated                  │
│  Diagnosis of exclusion                             │
└──────────────────────────────────────────────────────┘
         ↓
CLINICAL FEATURES (MEDICINE)

LOCAL EFFECTS:
• Central tumour: Haemoptysis, Cough, Stridor, Wheeze
• Bronchial obstruction: Atelectasis → Post-obstructive pneumonia
• Pleural invasion: Malignant effusion (bloodstained, exudate)

INVASION EFFECTS:
• Horner's syndrome (Pancoast — superior sulcus tumour):
  Ptosis + Miosis + Anhidrosis (sympathetic chain invaded)
• Hoarseness: Recurrent laryngeal nerve invasion (left side)
• SVC obstruction: Facial/arm oedema + distended neck veins
• Dysphagia: Oesophageal compression
• Phrenic nerve → Diaphragm paralysis

PARANEOPLASTIC (DISTANT, no metastasis):
SCLC:      SIADH → ↓ Na+ (hyponatraemia)
           Ectopic ACTH → Cushing's syndrome
           Eaton-Lambert (↑ strength with repetition — opposite MG)
Squamous:  PTHrP → Hypercalcaemia ("bones, moans, groans, stones")
Adeno:     HPOA → Clubbing + periosteal new bone
           (check ALL lung cancer patients for clubbing!)

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═══════════════════════════════════

THE MASTER COMBO FORMULA

═══════════════════════════════════

For EVERY DISEASE:

      CAUSE
        ↓
  MECHANISM          ← This is WHERE Medicine meets Pathology
  (biochemistry,         The mechanism explains BOTH
   immunology,           what you SEE under microscope
   haemodynamics)        AND what the patient FEELS
        ↓
   PATHOLOGY               MEDICINE
   (Gross + Microscopy)    (Symptoms + Signs + Ix)
   What you SEE            What you FEEL + FIND
        ↓                        ↓
       BOTH explained by the SAME mechanism
        ↓
   COMPLICATIONS
   (Pathology progresses → New clinical problems)

"[Disease] occurs when [CAUSE] leads to [MECHANISM].
This causes [PATHOLOGICAL CHANGE] seen as [gross/histological finding],
which explains the clinical features of [symptoms/signs].
Progression leads to [COMPLICATION] because [mechanism of complication]."

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