COMPLETE LEARNING NOTE

DRUG TREATMENT OF MYOCARDIAL INFARCTION AND ANGINA

From Zero to MBBS Examination Mastery

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SECTION 1: BIG PICTURE OVERVIEW

What Problem Are We Solving?

1. Reduce the heart's demand for oxygen (so what little oxygen arrives is enough)
2. Increase the supply of oxygen to the heart (by opening up blood vessels)
3. Prevent the clot from forming or growing (antiplatelet and anticoagulant drugs)
4. Dissolve an existing clot (thrombolytics)
5. Protect the surviving heart muscle after an attack (cardioprotective drugs)
6. Prevent another attack from happening (secondary prevention)

ANGINA = OXYGEN DEMAND > OXYGEN SUPPLY

TREATMENT = Decrease demand + Increase supply + Prevent/dissolve clot

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SECTION 2: BUILD THE FOUNDATION

2A. Normal Coronary Circulation (What is NORMALLY happening?)

• Left coronary artery (LCA): Splits into the Left Anterior Descending (LAD) artery and the Left Circumflex (LCx) artery. The LAD supplies the front wall of the left ventricle - the most powerful pumping chamber.
• Right coronary artery (RCA): Supplies the right ventricle and the bottom (inferior) wall of the left ventricle.

2B. What is Atherosclerosis? (Why do the pipes get blocked?)

Step 1: LDL cholesterol enters the arterial wall
        ↓
Step 2: LDL becomes oxidized (damaged by free radicals)
        ↓
Step 3: The vessel wall becomes inflamed - white blood cells rush in
        ↓
Step 4: Macrophages (white blood cells) eat the oxidized LDL
        ↓
Step 5: Macrophages become "foam cells" (fat-laden cells)
        ↓
Step 6: Foam cells die and deposit their fat - forming the fatty core
        ↓
Step 7: A fibrous cap (like a scab) forms over the fatty core
        ↓
Step 8: Over years, the plaque grows and narrows the vessel lumen
        ↓
Step 9: Narrowing reduces blood flow → ANGINA
        ↓
Step 10: If the fibrous cap RUPTURES → clot forms instantly → TOTAL BLOCKAGE → MI

• Stable plaque: Thick fibrous cap, hard, calcified. Causes STABLE ANGINA (chest pain only with exertion, relieved by rest).
• Unstable plaque: Thin fibrous cap, large lipid core, inflamed. Can rupture WITHOUT WARNING. Causes UNSTABLE ANGINA and MI.

2C. The Clot Formation Cascade (Why does a heart attack happen so suddenly?)

Plaque ruptures
    ↓
Subendothelial collagen and lipid core exposed to blood
    ↓
Platelets stick to exposed collagen (adhesion via vWF and GPIb receptor)
    ↓
Platelets become activated → release ADP, TXA2 (thromboxane A2), serotonin
    ↓
These chemicals recruit MORE platelets (amplification)
    ↓
Platelets aggregate together (aggregation via GPIIb/IIIa receptor + fibrinogen)
    ↓
Platelet plug forms ("white thrombus")

Tissue factor exposed at rupture site
    ↓
Tissue Factor + Factor VII → activates Factor X
    ↓
Factor X → converts prothrombin to THROMBIN
    ↓
Thrombin → converts fibrinogen to FIBRIN
    ↓
Fibrin mesh traps red blood cells → "red thrombus"
    ↓
Occlusive thrombus = COMPLETE BLOCKAGE = HEART ATTACK

2D. The Oxygen Supply-Demand Equation in Detail

1. Heart rate - faster heart = more oxygen needed per minute
2. Contractility - harder the heart squeezes = more oxygen used
3. Wall tension - larger the heart (more volume or pressure inside) = more wall tension = more oxygen needed (Laplace's Law: Tension = Pressure × Radius / Wall thickness)
4. Afterload - resistance the heart has to pump against (= blood pressure)

1. Coronary blood flow - depends on: diastolic blood pressure (coronary filling happens during diastole!), coronary artery diameter, heart rate (longer diastole = more filling time at lower heart rates)
2. Oxygen-carrying capacity of blood - hemoglobin levels, oxygen saturation

2E. Classification of Angina (Critical for exam)

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SECTION 3: DRUG CLASS FRAMEWORK

Overview of ALL Drug Classes Used

ANGINA / ACS DRUGS
│
├── A. Anti-ischemic Drugs (Reduce demand / Increase supply)
│   ├── 1. Nitrates (Organic nitrates)
│   ├── 2. Beta-blockers
│   ├── 3. Calcium Channel Blockers (CCBs)
│   └── 4. Ranolazine (late Na+ channel blocker)
│
├── B. Antiplatelet Drugs (Prevent platelet clot)
│   ├── 1. Aspirin (COX inhibitor)
│   ├── 2. P2Y12 inhibitors (Clopidogrel, Ticagrelor, Prasugrel)
│   └── 3. GPIIb/IIIa inhibitors (Abciximab, Eptifibatide, Tirofiban)
│
├── C. Anticoagulants (Prevent fibrin clot)
│   ├── 1. Unfractionated Heparin (UFH)
│   ├── 2. Low Molecular Weight Heparin (LMWH - Enoxaparin)
│   ├── 3. Fondaparinux
│   └── 4. Bivalirudin
│
├── D. Thrombolytics (Dissolve existing clot) - STEMI only
│   ├── 1. Streptokinase (SK)
│   ├── 2. Alteplase (tPA)
│   ├── 3. Tenecteplase (TNK-tPA)
│   └── 4. Reteplase
│
└── E. Secondary Prevention / Cardioprotective
    ├── 1. Statins (HMG-CoA reductase inhibitors)
    ├── 2. ACE Inhibitors / ARBs
    └── 3. Aldosterone Antagonists (Spironolactone, Eplerenone)

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DRUG CLASS 1: ORGANIC NITRATES

What are they?

Mechanism of Action - Step by Step

Nitrate drug taken by patient
    ↓
Nitrate converted to Nitric Oxide (NO) inside vascular smooth muscle cells
    (This conversion requires -SH groups; depletion of SH groups causes tolerance)
    ↓
NO activates enzyme: Guanylyl Cyclase
    ↓
Guanylyl cyclase converts GTP → cyclic GMP (cGMP)
    ↓
cGMP activates protein kinase G
    ↓
Protein kinase G → DECREASES intracellular calcium
    ↓
Less calcium → vascular smooth muscle RELAXES → blood vessel DILATES
    ↓
VENODILATION (at low doses) + ARTERIAL DILATION (at higher doses)

• More blood pools in the venous reservoir (periphery)
• Less blood returns to the heart (decreased preload/venous return)
• Heart has less volume to pump against
• Wall tension decreases (Laplace's Law)
• Oxygen demand falls dramatically
• This is the PRIMARY mechanism for effort angina relief

• Relieves coronary artery spasm (especially useful in Prinzmetal's angina)
• Increases collateral blood flow to ischemic areas
• Redistributes flow toward the subendocardium (the most vulnerable layer)

How Nitrates Reduce Oxygen Demand:

Nitrate
    ↓
Venodilation → ↓ Venous return → ↓ Preload → ↓ End-diastolic volume
    ↓
↓ Left ventricular volume → ↓ Wall tension (Laplace) → ↓ O2 demand
    ↓
Arterial dilation → ↓ Afterload (at higher doses) → ↓ O2 demand further
    ↓
Coronary dilation → ↑ O2 supply to ischemic areas

Classification of Nitrates

Adverse Effects of Nitrates

Nitrate Tolerance - The Critical Concept

Nitrate needs -SH (sulfhydryl) groups to be converted to NO
    ↓
Continuous nitrate → depletes -SH groups in vessel wall
    ↓
Less NO produced from same dose
    ↓
Less vasodilation → less effect = TOLERANCE

• Provide an 8-12 hour nitrate-free interval each day
• For patches: Apply in morning, remove at bedtime
• For ISMN: Asymmetric dosing (e.g., 8am and 2pm, NOT 8am and 8pm)
• Captopril (ACE inhibitor) may help prevent tolerance by restoring -SH groups

Nitrate Drug Interactions - THE MOST IMPORTANT!

Nitrates → increase cGMP (via NO → Guanylyl cyclase)
PDE5 inhibitors → BLOCK the enzyme that breaks down cGMP
    ↓
Both increase cGMP simultaneously → MASSIVE VASODILATION → PROFOUND HYPOTENSION
    ↓
Can cause fatal cardiovascular collapse

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DRUG CLASS 2: BETA-ADRENERGIC BLOCKERS (BETA-BLOCKERS)

What are they?

Types of Beta-Receptors

Mechanism of Action in Angina/MI

Beta-1 receptors blocked in the heart
    ↓
Heart rate decreases (negative chronotropy) → ↓ O2 demand
    ↓
Contractility decreases (negative inotropy) → ↓ O2 demand
    ↓
AV conduction slows → more time for ventricular filling
    ↓
Diastole lengthens → more time for coronary perfusion
    ↓
Blood pressure decreases → ↓ afterload → ↓ O2 demand
    ↓
Triple benefit: ↓ HR + ↓ Contractility + ↑ Coronary filling time

1. Reduce infarct size by limiting oxygen demand
2. Antiarrhythmic effect - MI causes dangerous arrhythmias (VF = the #1 cause of death in early MI). Beta-blockers stabilize the heart rhythm.
3. Prevent cardiac remodeling - After MI, the surviving heart muscle under stress from the sympathetic system undergoes harmful structural changes (dilation, fibrosis). Beta-blockers prevent this.
4. Reduce re-infarction risk - Proven mortality benefit in multiple large trials

Classification of Beta-Blockers

Adverse Effects of Beta-Blockers

Contraindications of Beta-Blockers

• Severe asthma / reactive airway disease
• 2nd or 3rd degree AV block (without pacemaker)
• Severe bradycardia (<50 bpm)
• Cardiogenic shock
• Decompensated heart failure with pulmonary edema (use WITH CAUTION once stabilized - carvedilol/bisoprolol reduce mortality in stable heart failure)

• COPD (use cardioselective)
• Insulin-dependent diabetes
• Peripheral vascular disease
• Variant (Prinzmetal) angina - THIS IS A TRAP! See below.

THE EXAM TRAP: Why are beta-blockers CONTRAINDICATED in Prinzmetal's angina?

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DRUG CLASS 3: CALCIUM CHANNEL BLOCKERS (CCBs)

What are they?

Mechanism:

Calcium enters cells through voltage-gated L-type calcium channels
    ↓
CCBs BLOCK these L-type channels
    ↓
Less calcium inside the cell
    ↓
EFFECT ON HEART: ↓ Heart rate + ↓ Contractility + Slowed AV conduction
EFFECT ON VESSELS: Smooth muscle relaxes → Vasodilation

Classification of CCBs - THE CRITICAL DISTINCTION

• Long half-life (~35-50 hours) → once-daily dosing
• Slow onset → NO reflex tachycardia
• Well-tolerated
• Proven benefit in stable angina

Clinical Uses of CCBs in Angina

1. Stable angina: All CCBs (especially amlodipine)
2. Variant (Prinzmetal) angina: CCBs are FIRST-LINE (along with nitrates)
3. Unstable angina: CCBs added when beta-blockers + nitrates are insufficient; Non-DHPs NOT combined with beta-blockers
4. Post-MI: Amlodipine/Diltiazem may be used IF beta-blockers contraindicated; Verapamil should be AVOIDED in MI with LV dysfunction

Adverse Effects of CCBs

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DRUG CLASS 4: ANTIPLATELET DRUGS

A. ASPIRIN (Acetylsalicylic Acid)

Mechanism:

Platelet activation requires TXA2 (Thromboxane A2)
TXA2 is made by enzyme COX-1 (Cyclooxygenase-1)
    ↓
Aspirin IRREVERSIBLY acetylates and inhibits COX-1
    ↓
NO TXA2 production in that platelet for its ENTIRE LIFESPAN (7-10 days!)
    ↓
Platelet cannot amplify its own activation signal
    ↓
Less platelet aggregation → less clot formation

• LOW dose (75-325 mg/day): Antiplatelet - preferentially blocks TXA2 in platelets more than PGI2 (prostacyclin) in vessels (PGI2 is anti-aggregatory; we want to keep it)
• HIGH dose (>325 mg/day): Anti-inflammatory + analgesic + antipyretic (inhibits COX-1 and COX-2)
• In ACS: Loading dose 325 mg (chewed, NOT swallowed whole - chewing gives faster absorption), then 75-100 mg daily indefinitely

Adverse Effects of Aspirin:

• GI irritation and bleeding - Most common. Aspirin damages gastric mucosa by: (1) direct irritation, (2) inhibition of prostaglandins that normally protect the stomach mucosa (PGE2/PGI2 stimulate mucus production and inhibit acid)
• Peptic ulcer disease exacerbation
• Hypersensitivity / Aspirin-induced asthma - COX-1 inhibition diverts arachidonic acid to the lipoxygenase pathway → more leukotrienes → bronchospasm in susceptible individuals
• Reye's syndrome - In children with viral infections (flu, chickenpox), aspirin use is ABSOLUTELY CONTRAINDICATED due to risk of Reye's syndrome (liver failure + encephalopathy)
• Bleeding - Including intracranial hemorrhage
• Tinnitus and deafness at HIGH (toxic) doses - due to cochlear effects

B. P2Y12 RECEPTOR INHIBITORS (ADP Receptor Blockers)

Clopidogrel (Plavix):

Clopidogrel → Pro-drug → metabolized by CYP2C19 in liver → Active metabolite
    ↓
Active metabolite IRREVERSIBLY blocks P2Y12 receptor on platelets
    ↓
ADP cannot bind to P2Y12 → Less platelet activation and aggregation

Ticagrelor (Brilinta):

• Does NOT require metabolic activation (active as given)
• REVERSIBLE P2Y12 blocker (unlike clopidogrel/prasugrel which are irreversible)
• Faster onset than clopidogrel
• Superior to clopidogrel (PLATO trial - 16% relative risk reduction in death/MI/stroke)
• Side effect unique to ticagrelor: Dyspnea (shortness of breath) - mechanism not fully understood; and also causes bradycardia
• Aspirin dose must not exceed 100 mg/day when combined with ticagrelor - high-dose aspirin reduces ticagrelor's efficacy (important!)
• Loading dose: 180 mg, then 90 mg twice daily

Prasugrel (Effient):

• Pro-drug, faster and more complete conversion to active form than clopidogrel
• IRREVERSIBLE P2Y12 blocker
• More potent and consistent than clopidogrel
• Higher bleeding risk (especially intracranial hemorrhage)
• CONTRAINDICATED in: Prior stroke/TIA, age ≥75, weight <60 kg (net harm in these groups)
• Loading dose: 60 mg, then 10 mg daily

C. GPIIb/IIIa INHIBITORS

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DRUG CLASS 5: ANTICOAGULANTS IN ACS

Unfractionated Heparin (UFH)

UFH binds to ANTITHROMBIN III (AT-III) in the blood
    ↓
AT-III is normally a natural clot inhibitor (works slowly)
    ↓
UFH binding ACCELERATES AT-III activity by 1000-fold!
    ↓
Activated AT-III inhibits: Thrombin (Factor IIa) AND Factor Xa
    ↓
No thrombin → no conversion of fibrinogen to fibrin → no clot growth

HIT - Heparin-Induced Thrombocytopenia (HIGH YIELD!)

Heparin binds to Platelet Factor 4 (PF4) → forms heparin-PF4 complex
    ↓
Immune system makes IgG antibodies against this complex
    ↓
IgG-heparin-PF4 complex activates platelets massively
    ↓
Platelet consumption → Thrombocytopenia (<100,000)
    ↓
BUT ALSO paradoxical THROMBOSIS (venous and arterial)
    ↓
"White clot syndrome" - clots form despite low platelets

1. STOP all heparin immediately (including heparin flushes, LMWH!)
2. Do NOT give platelets (worsens thrombosis)
3. Start alternative anticoagulation: Argatroban (direct thrombin inhibitor) or Fondaparinux
4. Can transition to warfarin ONLY after platelet count recovers (>150,000)

Low Molecular Weight Heparin (LMWH) - Enoxaparin

• Subcutaneous injection (not IV infusion)
• Predictable response (no monitoring needed in most patients)
• Less binding to plasma proteins
• Lower risk of HIT
• Can be used as outpatient

Fondaparinux

Bivalirudin

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DRUG CLASS 6: THROMBOLYTICS (FIBRINOLYTICS)

Thrombolytic drug
    ↓
Activates PLASMINOGEN → converts to PLASMIN
    ↓
Plasmin is a protease that digests FIBRIN (the mesh of the clot)
    ↓
Clot dissolves → coronary artery reopens → blood flow restored
    ↓
Heart muscle saved from death

• When PCI is NOT available within 120 minutes of first medical contact
• Door-to-balloon time >120 min → give thrombolysis

1. Derived from Group C beta-hemolytic Streptococci → can cause allergic reactions (fever, anaphylaxis)
2. ANTIGENIC - body forms anti-SK antibodies after use → CANNOT be given again within 5 days to 12 months (usually say avoid for at least 1 year, some sources say 12 months)
3. CHEAPEST thrombolytic (important in low-resource settings)
4. May cause hypotension (histamine release)

• Previous intracranial hemorrhage (any time)
• Ischemic stroke within 3 months
• Known structural cerebrovascular lesion (AVM, aneurysm, tumor)
• Active bleeding (excluding menses)
• Aortic dissection (NEVER give - will extend dissection!)
• Closed head injury within 3 months
• Severe uncontrolled hypertension (SBP >180 or DBP >110) at time of giving

• Prior ischemic stroke >3 months ago
• Traumatic CPR >10 minutes
• Major surgery within 3 weeks
• Internal bleeding within 2-4 weeks
• Pregnancy
• Active peptic ulcer disease
• Previous streptokinase use (5 days to 12 months) - for SK specifically

1. Relief of chest pain

2. 50% reduction of ST elevation at 90 minutes

3. Reperfusion arrhythmias (most commonly Accelerated Idioventricular Rhythm (AIVR) - benign, usually self-terminating) within 2 hours of drug completion
4. Early peak of cardiac enzymes (washout effect)

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DRUG CLASS 7: STATINS (HMG-CoA REDUCTASE INHIBITORS)

Why are statins used in MI/Angina?

1. Lower LDL cholesterol - slows and can stabilize/reverse plaque growth
2. Plaque stabilization - most important for ACS! Statins make plaques LESS LIKELY TO RUPTURE by reducing the lipid core, increasing the fibrous cap thickness, and reducing inflammation
3. Endothelial function improvement - increase NO production from endothelium

Mechanism:

Normally: HMG-CoA → (HMG-CoA Reductase) → Mevalonate → Cholesterol
    ↓
Statin INHIBITS HMG-CoA Reductase (the rate-limiting enzyme)
    ↓
Less cholesterol made in liver cells
    ↓
Liver cells "sense" low cholesterol → upregulate LDL receptors on surface
    ↓
More LDL receptors grab LDL from the bloodstream
    ↓
Serum LDL drops dramatically

Adverse Effects of Statins:

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DRUG CLASS 8: ACE INHIBITORS / ARBs

Why in MI?

1. Activating the RAAS (Renin-Angiotensin-Aldosterone System)
2. Angiotensin II causes vasoconstriction, sodium retention, aldosterone release
3. This leads to cardiac remodeling - the healthy heart muscle enlarges and changes shape (dilates, thickens walls abnormally)
4. Eventually → Heart failure

Mechanism:

Angiotensinogen → (Renin) → Angiotensin I → (ACE) → Angiotensin II
    ↓
ACE Inhibitor BLOCKS ACE enzyme
    ↓
No Angiotensin II → No vasoconstriction → BP falls
    ↓
No Angiotensin II → No Aldosterone → Less sodium retention, less fluid overload
    ↓
Reduced cardiac remodeling → Preserved left ventricular function → Better survival

• LV ejection fraction ≤40% (systolic dysfunction)
• Heart failure features
• Anterior MI (largest territory)
• Hypertension or diabetes

The Dry Cough of ACE Inhibitors:

ACE enzyme also breaks down BRADYKININ (normally)
    ↓
ACE inhibitor → ACE blocked → Bradykinin NOT broken down → accumulates
    ↓
Bradykinin in lungs → irritates airway → DRY COUGH
    ↓
Occurs in up to 10-15% of patients (more common in Asians)
    ↓
Switch to ARB (ARBs block Angiotensin receptor, not ACE, so bradykinin is unaffected)

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DRUG CLASS 9: RANOLAZINE

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SECTION 4: ANALOGIES TO MAKE YOU NEVER FORGET

1. Nitrates - "The Parking Lot Analogy"

2. Beta-Blockers - "The Emergency Brake"

3. Calcium Channel Blockers - "The Power Switch"

4. Aspirin - "The Permanent Tattoo"

5. Clopidogrel - "The Broken Lock Analogy"

6. Heparin - "The Supercharger for the Security Guard"

7. Streptokinase - "The Molecular Crowbar"

8. Statins - "The Factory Output Reducer"

9. The ACE Inhibitor - "The RAAS Dam"

10. HIT - "The Friendly Fire Disaster"

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SECTION 5: STEP-BY-STEP CLINICAL REASONING

Case 1: STEMI - How a Doctor Thinks

• YES → Primary PCI (preferred) → antiplatelet + anticoagulant + transfer urgently
• NO → Thrombolysis (if no contraindications) within 30 min of hospital arrival ("door-to-needle")

• Beta-blocker: Oral metoprolol 25-50 mg (if no contraindications - no bradycardia, no heart block, no acute LV failure, no bronchospasm)
• P2Y12: Ticagrelor 180 mg loading (preferred over clopidogrel if going for PCI) OR Clopidogrel 600 mg
• Anticoagulant: UFH (60 units/kg IV bolus, max 4000 units, then infusion) or Enoxaparin or Fondaparinux

1. Aspirin 75 mg daily - indefinitely
2. Ticagrelor 90 mg twice daily (or Clopidogrel 75 mg daily) - for at least 12 months after ACS
3. Beta-blocker (Metoprolol/Bisoprolol) - indefinitely (reduces remodeling, mortality, arrhythmia)
4. ACE inhibitor (Ramipril/Lisinopril) - especially if EF <40%, hypertension, diabetes
5. High-intensity Statin (Atorvastatin 80 mg) - indefinitely
6. Eplerenone/Spironolactone - if EF ≤40% with heart failure features

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Case 2: Stable Angina - A Different Scenario

• Beta-blocker (Metoprolol/Atenolol) - FIRST LINE - reduces symptoms AND future MI/death
• If beta-blocker not tolerated or contraindicated → Long-acting CCB (Amlodipine)
• If single drug not enough → Combination (Beta-blocker + DHP CCB like Amlodipine) OR (Beta-blocker + Long-acting nitrate)
• CAUTION: Beta-blocker + Non-DHP CCB (Verapamil/Diltiazem) is dangerous - can cause complete heart block

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Case 3: The Unstable Angina / NSTEMI

1. ASPIRIN 300 mg loading + 75 mg daily
2. P2Y12 inhibitor - Ticagrelor (preferred) or Clopidogrel
3. Anticoagulant - Fondaparinux (preferred in NSTEMI per guidelines, lower bleeding risk) OR LMWH OR UFH
4. Beta-blocker - Metoprolol orally (if no contraindications)
5. Nitrates - GTN SL for pain; IV if persistent chest pain
6. Statin - High intensity immediately
7. ACE inhibitor - Especially if EF reduced, hypertension, diabetes
8. Risk stratification - GRACE score or TIMI score → Decide timing of coronary angiography

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SECTION 6: MEMORY TOOLS

MNEMONIC 1: THE STEMI IMMEDIATE TREATMENT - "BATMAN"

• B - Beta-blocker (if no contraindications)
• A - Aspirin 300 mg (chewed)
• T - Ticagrelor (or clopidogrel) loading dose
• M - Morphine (for pain) + Monitor (continuous ECG, pulse oximetry)
• A - Anticoagulant (Heparin/LMWH/Fondaparinux)
• N - Nitrates (GTN sublingual/IV) + iNterventional: PCI or Thrombolysis

MNEMONIC 2: POST-MI LONG-TERM THERAPY - "BASIC"

• B - Beta-blocker
• A - Aspirin + Another antiplatelet (DAPT x 12 months)
• S - Statin (high intensity)
• I - Inhibitor of ACE (ACE inhibitor or ARB)
• C - Carbonic aldosterone antagonist (Eplerenone if indicated)

MNEMONIC 3: CONTRAINDICATIONS TO NITRATES - "VERY HIGH PRESSURE PATIENTS SHOULD STOP"

• Ventricular outflow obstruction (HOCM, severe aortic stenosis)
• Hypotension (SBP <90)
• PDE5 inhibitors (Sildenafil, Tadalafil) taken in last 24-48 hours
• Sildenafil (same as above - worth double-emphasizing!)
• RV infarction (Right ventricular)

MNEMONIC 4: THROMBOLYTIC ABSOLUTE CONTRAINDICATIONS - "ABCDE"

• A - Aortic dissection, Active internal bleeding
• B - Brain tumor / structural lesion (AVM, aneurysm)
• C - Closed head injury (recent <3 months)
• D - Diastolic BP >110 AND Systolic >180 (uncontrolled HTN)
• E - Earlier hemorrhagic stroke (any time) / earlier ischemic stroke (<3 months)

MNEMONIC 5: DIFFERENTIATING CCBs - "VASCULAR vs CARDIAC"

MNEMONIC 6: REMEMBER ASPIRIN'S MECHANISM - "PERMANENT ACE"

MNEMONIC 7: WHICH ANTIPLATELET? "CTP"

• Clopidogrel - needs CYP2C19 activation, beware omeprazole interaction
• Ticagrelor - most commonly preferred in ACS (PLATO trial winner), dyspnea side effect
• Prasugrel - most potent, but contraindicated in prior stroke/TIA, elderly, low weight

RAPID REVIEW TABLE: DRUGS IN STABLE ANGINA

RAPID REVIEW TABLE: DRUGS IN ACS/STEMI

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SECTION 7: EXAMINER'S CORNER

Most Frequently Tested Facts

1. Mechanism of action of nitroglycerin - GTN → NO → cGMP → smooth muscle relaxation → venodilation → ↓ preload
2. Why sublingual GTN? - Avoids first-pass metabolism; rapid onset (1-2 min)
3. Nitrate tolerance - Mechanism (-SH depletion), Prevention (nitrate-free interval 8-10 hours)
4. Contraindication: Nitrates + Sildenafil - Both increase cGMP → catastrophic hypotension
5. Beta-blocker contraindication in Prinzmetal angina - Unopposed alpha-mediated spasm
6. Short-acting nifedipine avoided in angina - Reflex tachycardia worsens ischemia
7. Aspirin mechanism - Irreversible COX-1 inhibition → blocks TXA2
8. Why chew aspirin in MI? - Faster absorption, quicker platelet inhibition
9. Clopidogrel + omeprazole interaction - Both use CYP2C19; omeprazole reduces clopidogrel activation
10. Streptokinase - cannot repeat - Antibodies formed; also can cause allergy
11. HIT-2 - Heparin-PF4-IgG → paradoxical thrombosis despite thrombocytopenia; stop heparin; treat with argatroban
12. Thrombolytics contraindicated in NSTEMI - No total occlusion; increases bleeding without benefit
13. ACE inhibitor cough - Bradykinin accumulation; switch to ARB
14. DAPT duration after ACS - Minimum 12 months (aspirin + P2Y12 inhibitor)
15. Protamine reverses heparin - Not LMWH (only partial); not fondaparinux (no reversal)

Most Likely Essay Questions

1. "Describe the pharmacological management of Acute Myocardial Infarction."
2. "Discuss the drugs used in the treatment of angina pectoris. Compare stable and unstable angina treatment."
3. "Describe the mechanism of action, clinical uses, adverse effects, and drug interactions of organic nitrates."
4. "Write an essay on antiplatelet drugs used in ischemic heart disease."
5. "Discuss the role of thrombolytics in STEMI. Name the drugs, their mechanisms, and contraindications."

Most Likely Short Notes

1. Nitrate tolerance - mechanism and prevention
2. Adverse effects of beta-blockers
3. Aspirin mechanism of action in ACS
4. Contraindications of thrombolytics
5. Heparin-induced thrombocytopenia (HIT)
6. Compare Clopidogrel vs Ticagrelor
7. Role of statins in ACS
8. ACE inhibitors post-MI
9. Prinzmetal angina - treatment
10. Why is short-acting nifedipine avoided in angina?

Most Likely Viva Questions

• "Why do we use sublingual route for GTN?" (Avoids first-pass; rapid onset)
• "What is the mechanism of nitrate tolerance? How do you prevent it?" (SH depletion; nitrate-free interval)
• "Why is aspirin given as a chewed tablet in MI?" (Faster absorption for immediate antiplatelet effect)
• "Why can't you repeat streptokinase within 12 months?" (Antibody formation → allergic reaction + reduced efficacy)
• "What happens if you give nitrates to someone who has taken sildenafil?" (Massive hypotension via cGMP accumulation)
• "Why are beta-blockers contraindicated in Prinzmetal angina?" (Block Beta-2 → unopposed Alpha → worsens spasm)
• "What is the reperfusion marker after thrombolysis?" (ST resolution >50% at 90 min; reperfusion arrhythmia - AIVR; pain relief)
• "What is the antidote for heparin? Does it work for LMWH?" (Protamine - fully reverses UFH, only ~60% LMWH)
• "Why is fondaparinux not used alone during PCI?" (No anti-IIa effect → catheter thrombosis risk)
• "Which beta-blocker is used in acute MI given IV?" (Metoprolol; Esmolol for rate control in acute settings)

Most Likely MCQs

• A) Use alteplase instead ✓ (SK antibodies present - cannot repeat)
• B) SK can be given at double dose
• C) SK is the only thrombolytic, proceed anyway
• D) Give with antihistamine first

• A) Beta-blocker
• B) Calcium channel blocker + Nitrate ✓
• C) Aspirin alone
• D) Propranolol

• A) Omeprazole
• B) Esomeprazole
• C) Pantoprazole ✓ (least CYP2C19 inhibition)
• D) Lansoprazole

• A) Irreversible COX-1 inhibitor
• B) Reversible P2Y12 receptor antagonist ✓
• C) GPIIb/IIIa inhibitor
• D) Thrombin inhibitor

• A) Age >75 years
• B) Prior ischemic stroke 4 months ago
• C) Previous hemorrhagic stroke ✓
• D) Prolonged CPR for 12 minutes

• A) Nitrates are teratogenic with long use
• B) Continuous use depletes SH groups, causing tolerance ✓
• C) Nitrates accumulate and cause hepatotoxicity
• D) Reflex tachycardia is prevented this way

• A) Aspirin
• B) Morphine
• C) Nitrates ✓ (RV infarct is preload-dependent - nitrates further reduce preload → catastrophic hypotension)
• D) Beta-blockers

• A) Thrombocytopenia
• B) Dyspnea ✓
• C) Constipation
• D) Nephrotoxicity

Common Exam TRAPS

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SECTION 9: HIGH-YIELD REVISION SHEET

ONE-PAGE RAPID REVISION

BIG PICTURE

• Angina = O2 demand > O2 supply in the myocardium
• Stable angina = fixed plaque (>70% stenosis); Exertional pain; relieved by rest
• Unstable angina / NSTEMI = plaque rupture + partial occlusion; Rest pain; ECG: ST depression
• STEMI = total occlusion; ECG: ST elevation; Troponin elevated; EMERGENCY

MUST-KNOW MECHANISMS

MUST-KNOW TOXICITIES

EXAM EMERGENCY FACTS

1. GTN + Sildenafil = LETHAL COMBINATION (Absolute CI)
2. Beta-blockers WORSEN Prinzmetal angina (use CCB + nitrates instead)
3. Short-acting nifedipine AVOIDED in angina (reflex tachycardia)
4. Streptokinase cannot be repeated within 12 months (antibody formation)
5. THROMBOLYTICS ARE CONTRAINDICATED IN NSTEMI (only STEMI gets them)
6. Aortic dissection is an ABSOLUTE CONTRAINDICATION to thrombolytics
7. HIT type 2: PARADOXICAL THROMBOSIS despite low platelets; treat with argatroban, not platelets
8. Aspirin dose matters with ticagrelor: Keep aspirin ≤100 mg/day (higher dose reduces ticagrelor effect)
9. Fondaparinux needs UFH added during PCI (catheter thrombosis prevention)
10. Post-MI DAPT = 12 months minimum (aspirin + P2Y12 inhibitor)
11. Post-MI lifelong = BASIC (Beta-blocker + Aspirin + Statin + ACE inhibitor ± aldosterone antagonist)
12. Protamine: Fully reverses UFH; only ~60% reverses LMWH; does NOT reverse fondaparinux
13. GTN CONTRAINDICATED in RV infarct (inferior MI + hypotension → suspect RV infarct)
14. Beta-blocker withdrawal = NEVER abrupt (rebound sympathetic stimulation → MI)
15. Verapamil + Beta-blocker = dangerous (both slow heart rate + AV conduction → heart block)

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SECTION 10: SELF-ASSESSMENT

10 Short-Answer Questions with Full Explanations

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• TXA2 pathway: Aspirin blocks COX-1 → no TXA2 → blocks this pathway
• ADP pathway: P2Y12 inhibitors block the ADP receptor → blocks this pathway

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1. PLATO trial showed ticagrelor reduced cardiovascular death, MI, and stroke by 16% compared to clopidogrel
2. Faster onset is critical in STEMI (time = muscle)
3. More predictable effect (no genetic polymorphism issue)
4. Not affected by PPI use (unlike clopidogrel)

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1. High oxygen concentrations cause vasoconstriction (hyperoxia paradoxically causes coronary vasoconstriction, reducing oxygen delivery to ischemic areas)
2. Excessive oxygen generates free radicals, worsening reperfusion injury
3. Some trials showed increased infarct size and no mortality benefit with routine oxygen in normoxic patients

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• STEMI = complete occlusion of a coronary artery by a thrombus = full ST elevation = indication for thrombolysis (if PCI unavailable)
• NSTEMI = partial occlusion OR complete occlusion of a smaller branch = NO ST elevation = NO indication for thrombolytics

1. The artery is not completely blocked; the patient has some residual flow. Thrombolytics do not improve outcomes when there is still some flow.
2. Thrombolytics actually worsen outcomes in NSTEMI - they can ACTIVATE platelets (paradoxical effect), cause plaque hemorrhage, extend the thrombus, and increase the risk of MI.
3. Clinical trials (TIMI-IIIB, GUSTO-IIb) showed higher rates of adverse outcomes with thrombolytics in NSTEMI.

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Sources

• Katzung's Basic and Clinical Pharmacology, 16th Edition (GTN mechanisms, nitrate effects, CCB classification)
• Goodman & Gilman's The Pharmacological Basis of Therapeutics (antianginal drug mechanisms)
• The Washington Manual of Medical Therapeutics (STEMI protocols, drug dosing tables, anticoagulant management)
• Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine (ischemic heart disease)
• Robbins & Kumar Basic Pathology (atherosclerosis, IHD pathology)
• Harrison's Principles of Internal Medicine, 22nd Edition (vasospastic angina, clinical management)
• Recent evidence: Tscharre M, et al. Antiplatelet therapy with clopidogrel versus aspirin in atherosclerotic cardiovascular disease: a systematic review and meta-analysis. Atherosclerosis, 2025 [PMID: 40845727]

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