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🫀 Guyton & Hall Physiology - Chapter 19

Role of the Kidneys in Long-Term Regulation of Arterial Pressure & Hypertension

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1. THE BIG CONCEPT: Why Kidneys Are the Ultimate BP Controller

• Short-term BP control = baroreceptors, vasomotor center, vasoconstriction (nervous system) - acts in seconds to minutes
• Long-term BP control = kidneys - acts over days, weeks, months
• The kidney is unique: it is the only mechanism with "infinite gain" for pressure control
  • "Infinite gain" = given enough time, the kidney can return BP to exactly normal, not just approximate it
  • All other controllers (baroreceptors, chemoreceptors) reset and lose effectiveness over time - the kidney never fully resets

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2. THE RENAL-BODY FLUID SYSTEM (Fundamental Concept)

1. ↑ Blood volume → ↑ Arterial pressure
2. ↑ Arterial pressure → ↑ Renal fluid/salt excretion (pressure diuresis + pressure natriuresis)
3. ↑ Excretion → ↓ Blood volume → pressure returns to normal

• A rise of just a few mm Hg can double urine water output (pressure diuresis) AND double salt output (pressure natriuresis)

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3. PRESSURE NATRIURESIS & PRESSURE DIURESIS (Mechanisms)

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4. EQUILIBRIUM POINT CONCEPT (The "Set Point" of BP)

• On a graph: Renal Output Curve vs Fluid Intake Line (horizontal)
• They intersect at ONE point = the equilibrium arterial pressure = the body's set point
• This is the only pressure at which output = intake - BP will always drift back here
• If intake ↑ → temporary fluid gain → BP rises → kidneys excrete more → new equilibrium at same pressure
• This is why the kidneys have "infinite gain" - the equilibrium point does not drift

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5. WHY INCREASED TOTAL PERIPHERAL RESISTANCE (TPR) ALONE CANNOT CAUSE CHRONIC HYPERTENSION

• If TPR ↑ but kidneys are normal → momentary BP rise → kidneys excrete more fluid → blood volume falls → BP returns to normal within days
• Chronic hypertension requires either:
  1. A shift in the renal pressure-natriuresis curve (kidney excretes LESS at any given pressure), OR
  2. ↑ Fluid/salt intake beyond what kidneys can handle

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6. RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (RAAS) AND BP CONTROL

Components

Three stimuli for renin release:

1. Baroreceptors in JG cells - sense ↓ stretch (= ↓ pressure) in afferent arteriole
2. Macula densa - senses ↓ NaCl delivery to early distal tubule
3. Sympathetic NS - beta-adrenergic receptors on JG cells → ↑ renin

Actions of Angiotensin II:

• Fast (vasoconstriction): ↑ arteriolar resistance → ↑ BP within seconds
• Slow (volume retention):
  • ↑ Na⁺/water reabsorption directly in tubules
  • ↑ Aldosterone secretion (adrenal cortex) → ↑ Na⁺ reabsorption in collecting duct
  • ↓ GFR (constricts efferent > afferent arteriole)

Rapidity of RAAS response:

• Vasoconstrictor effect: peaks in ~20 minutes
• Volume retention effect: takes hours to days
• Together, prevents BP from dropping after hemorrhage, salt restriction, etc.

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7. ROLE OF RAAS IN MAINTAINING NORMAL ARTERIAL PRESSURE

• If salt intake drops → less Na⁺ delivered to macula densa → ↑ renin → ↑ Ang II → vasoconstriction + volume retention → BP stays normal
• RAAS prevents the BP from falling with:
  • Low salt diet
  • Hemorrhage
  • Upright posture (orthostatic stress)
• ACE inhibitors / ARBs block this system → ↓ BP (especially effective in high-renin states)

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8. TYPES OF RENAL HYPERTENSION

A. Volume-Loading Hypertension (reduced kidney mass + high salt)

• ↓ Kidney mass (e.g., one kidney removed) + ↑ salt intake → kidneys cannot excrete enough → fluid accumulates → ↑ BP
• Two phases:
  1. Early phase: ↑ cardiac output (CO) drives the ↑ BP; TPR normal or low
  2. Late phase (weeks-months): CO returns toward normal, but TPR rises (autoregulatory vasoconstriction) - this is called "autoregulatory hypertension"
  • Blood vessels constrict to protect tissues from excess flow → TPR ↑ → maintains high BP even as CO normalizes

B. Hypertension from Excess Aldosterone (Primary Aldosteronism / Conn's Syndrome)

• Adrenal tumor secretes excess aldosterone
• Aldosterone → ↑ Na⁺/water reabsorption → ↑ blood volume → ↑ BP
• Early: ↑ CO; Late: ↑ TPR (autoregulation)
• If sustained → structural kidney changes → worsens further
• High salt diet makes it worse

C. Hypertension from Renin-Angiotensin System (Renovascular Hypertension)

• Clip on renal artery of one kidney, other kidney removed
• Clipped kidney: ↓ pressure → ↑ renin → ↑ Ang II → vasoconstriction + Na⁺ retention
• Short term: ↑ Ang II causes vasoconstriction → ↑ BP
• Long term: ↑ BP pressure natriuresis in the clipped kidney is impaired (because of low perfusion pressure past the clip), so Na⁺ retained → ↑ blood volume maintains hypertension
• Renin levels normalize over time but hypertension persists (now volume-dependent)

• Clip on one renal artery; contralateral kidney is normal
• Clipped kidney: ↓ pressure → ↑ renin → ↑ Ang II → vasoconstriction → ↑ BP
• Normal kidney: faces elevated BP → pressure natriuresis → excretes excess Na⁺ and water
• Result: volume stays nearly normal, but ↑ renin/Ang II drives sustained hypertension
• Renin levels remain elevated (unlike one-kidney model)
• This model mimics renal artery stenosis in humans with normal contralateral kidney

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9. PRIMARY (ESSENTIAL) HYPERTENSION (~90-95% of all hypertension)

1. Obesity/excess adiposity - accounts for 65-75% of risk
   • ↑ CO (extra blood flow to adipose tissue)
   • ↑ SNS activity (kidneys) → impairs pressure natriuresis
   • Leptin from fat cells → stimulates hypothalamus → ↑ vasomotor center activity
   • ↓ Baroreceptor sensitivity
   • ↑ Ang II and aldosterone
2. Sympathetic activation impairs the kidney's ability to excrete Na⁺ at normal pressures → renal function curve shifts rightward → new equilibrium at higher BP
3. Genetic factors (monogenic hypertension):
   • All known mutations → impaired kidney function (either ↑ renal arterial resistance OR ↑ tubular Na⁺ reabsorption)
   • Monogenic hypertension is RARE (<1% of all hypertension)
   • Key point: all monogenic hypertension = final common pathway = impaired renal Na⁺/water excretion
4. Structural kidney changes:
   • Over time, hypertension damages kidneys → ↑ preglomerular resistance → ↓ glomerular membrane permeability → worsens hypertension (vicious cycle)

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10. INTEGRATED SUMMARY: "Guiding Principle"

The kidneys set the long-term arterial pressure. Every form of chronic hypertension ultimately requires either a shift in the renal pressure-natriuresis curve to the right, or increased fluid/salt intake. The nervous system, hormones (RAAS, aldosterone), and structural kidney changes all affect BP through the kidneys.

Three ways to shift the renal function curve rightward (causing hypertension):

1. ↑ Ang II / aldosterone → ↑ tubular reabsorption
2. ↑ Renal sympathetic nerve activity → ↑ renal vascular resistance + ↑ tubular reabsorption
3. Structural kidney disease → ↓ nephron mass, ↓ filtration surface

Treatment logic:

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11. HIGH-YIELD SUMMARY TABLE

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1. Definitions - CO vs VR, why they must be equal
2. Normal values - 5 L/min, cardiac index 3 L/min/m², age effects, obesity caveat
3. Frank-Starling - the heart is a slave to VR; peripheral circulation controls CO, not the heart
4. CO = sum of tissue flows - metabolism drives everything
5. Limits to CO - upper limits, when the heart actually becomes the bottleneck
6. Hypereffective vs Hypoeffective heart - what shifts the cardiac output curve up vs down
7. Pathological high-CO states (AV fistula, anemia, hyperthyroid, beriberi, sepsis) vs low-CO
8. Nervous system - SNS effects on heart AND Psf
9. Cardiac Output Curves - intrapleural pressure, tamponade shifts (with real diagram)
10. Venous Return Curves - full explanation of plateau, downslope, zero-point (with real diagram)
11. Mean Systemic Filling Pressure - definition, normal = 7 mmHg, the formula, what changes it
12. Resistance to Venous Return - why veins dominate (2/3), the formula
13. Combined analysis (equilibrium point) - the intersection diagram with worked scenarios (blood volume, SNS, AV fistula) - with real diagram
14. Measurement methods - Fick, dye dilution formula, echo, bioimpedance (with error rates)
15. Exercise - how Psf rises to 30 mmHg, RVR falls, and CO hits 25-35 L/min
16. Master summary table - every factor + mechanism
17. Key numbers - everything you need to memorize
18. Concept map - the full circular logic in one diagram

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🫀 GUYTON & HALL — CHAPTER 21

THE CORONARY CIRCULATION

Brutal fact upfront: ~1/3 of all deaths in industrialized countries = coronary artery disease. Most older adults have SOME coronary impairment. This is clinically the most important chapter in cardiovascular physiology.

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📌 SECTION 1: PHYSIOLOGICAL ANATOMY OF CORONARY BLOOD SUPPLY

🔴 Coronary Arteries - Layout

• Main coronary arteries lie on the surface (epicardial)
• Smaller arteries penetrate inward through the muscle mass
• The inner 0.1 mm of endocardium can get nutrition directly from ventricular blood - but this is negligible
• Virtually ALL cardiac nutrition depends on the epicardial coronary arteries

🔵 Coronary Venous Drainage

🟠 Epicardial vs. Subendocardial Vasculature

• Epicardial arteries = large surface vessels - supply most of the muscle
• Intramuscular arteries = penetrate from epicardial arteries
• Subendocardial arterial plexus = extra plexus right beneath endocardium
  • During systole, these are maximally compressed by contracting LV muscle
  • The extra subendocardial plexus vessels normally compensate for systolic compression
  • BUT: under ischemic conditions, subendocardium is the FIRST to infarct (explained later)

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📌 SECTION 2: NORMAL CORONARY BLOOD FLOW VALUES

Note: The heart's work increases 6-9× during strenuous exercise, but coronary flow only increases 3-4×. The heart compensates by increasing its energy efficiency - it extracts more O₂ and uses substrates more efficiently.

Sex difference: Coronary blood flow per gram of heart tissue is typically higher in women than men, though women's hearts are smaller.

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📌 SECTION 3: PHASIC CORONARY BLOOD FLOW (Systole vs. Diastole)

LEFT VENTRICLE:
During SYSTOLE  → coronary capillary flow FALLS TO LOW LEVELS
During DIASTOLE → coronary capillary flow is HIGH (up to 4-5× systolic)

Reason: LV muscle contraction compresses intramuscular vessels → 
        blocks flow during systole

• RV muscle contracts with far less force than LV
• So phasic changes in RV coronary flow are only partial (not as dramatic)

Clinical implication: The heart receives most of its blood during DIASTOLE. When heart rate rises, diastolic filling time is disproportionately shortened → heart can become ischemic even with normal coronary arteries at very high heart rates.

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📌 SECTION 4: CONTROL OF CORONARY BLOOD FLOW

🔴 PRIMARY Controller: Local Muscle Metabolism (MOST IMPORTANT)

The heart controls its own blood supply through metabolic vasodilation. When work ↑, O₂ demand ↑ → local vasodilators released → arterioles dilate → flow ↑ proportionally.

• Normal: 70% of O₂ is extracted from coronary arterial blood at rest
• This is enormously high compared to most tissues (which extract ~25%)
• Result: almost no O₂ reserve - the only way to supply more O₂ is to increase flow
• Blood delivered to resting LV: ~8 mL O₂/100g/min
• Minimum to keep muscle alive: ~1.3 mL O₂/100g/min

Warning: Pharmacological agents that block adenosine do NOT fully prevent coronary vasodilation during exercise - meaning NO single substance is fully responsible. It is a multi-factor system.

1. During ischemia: ATP → ADP → AMP → Adenosine
2. Adenosine dilates vessels (good - tries to restore flow)
3. BUT adenosine also diffuses OUT of the cell
4. After 30 min of severe ischemia → ~50% of the adenine base is LOST from cells
5. New adenine synthesis rate = only 2%/hour
6. Therefore: if ischemia persists >30 min → even restoring flow may be too late to save cells
7. This is a MAJOR cause of irreversible cardiac cell death in MI

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🔵 SECONDARY Controller: Nervous System

Indirect Nervous Effects (more important):

• Sympathetic stimulation → ↑ HR + ↑ contractility → ↑ O₂ demand → local metabolic vasodilation overrides → net effect = ↑ coronary flow
• Vagal stimulation → ↓ HR + ↓ contractility → ↓ O₂ demand → indirect coronary vasoconstriction

Direct Nervous Effects (less important):

Clinically dangerous: In some people, alpha vasoconstrictor effects are disproportionately severe → coronary vasospasm during excess sympathetic activation → ischemia → angina. This is Prinzmetal (variant) angina. Triggers: emotional stress, cocaine/amphetamines, cold exposure, tobacco.

Key rule: Metabolic control ALWAYS overrides direct nervous vasoconstriction within seconds. You cannot starve the heart of flow by nervous means if the heart is actively working.

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📌 SECTION 5: SPECIAL FEATURES OF CARDIAC MUSCLE METABOLISM

⚡ Energy Substrates

• At REST: ~70% from fatty acids, ~30% from glucose/lactate/other
• During ISCHEMIA: forced to use anaerobic glycolysis → glucose consumed rapidly + lactic acid accumulates → contributes to ischemic chest pain

⚡ ATP and the Adenosine Cycle

• 95% of energy → produced as ATP in mitochondria

• ATP → chemical energy for contraction + all cellular functions
• Severe ischemia: ATP → ADP → AMP → Adenosine
  • Adenosine diffuses out → attempts to vasodilate (good)
  • But intracellular adenine stores depleted → can't regenerate ATP (bad → cell death)

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📌 SECTION 6: ISCHEMIC HEART DISEASE

Who gets it?

• ~35% of Americans aged ≥65 years die from ischemic heart disease
• Obstructive coronary atherosclerosis = most common cause
• Women: lower prevalence of obstructive atherosclerosis than men (especially pre-menopause) BUT sex difference attenuates with age → remains the #1 killer in women too
• Coronary microvascular dysfunction and vasospasm cause ischemia even with NO obstructive plaques on angiogram

Atherosclerosis (Brief):

• Genetic predisposition + obesity + sedentary lifestyle + hypertension + endothelial damage
• Cholesterol deposits → fibrous invasion → calcification → plaque → partial or complete luminal obstruction
• Most common site: first few centimeters of major coronary arteries

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📌 SECTION 7: ACUTE CORONARY ARTERY OCCLUSION

Two Main Mechanisms:

• Plaque breaks through endothelium → contacts blood
• Platelets adhere → fibrin deposits → RBCs trapped → thrombus grows → occlusion
• If thrombus breaks free and flows distally → coronary embolus

• Direct smooth muscle irritation by atherosclerotic plaque edges
• Or local neural reflexes → excessive wall contraction
• Triggers: extreme emotional stress, cocaine, amphetamines, tobacco, cold exposure
• Can lead to secondary thrombosis
• Treatment: calcium channel blockers + nitrates (vasodilators)

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🔴 Collateral Circulation - The Life-Saving Variable

How much heart muscle dies after occlusion depends enormously on collateral circulation.

• Large coronary arteries: almost NO major anastomoses
• Small arteries (20-250 µm): many anastomoses exist

• Collaterals develop gradually alongside the narrowing
• Person may NEVER experience an acute episode
• But eventually: atherosclerosis outpaces collateral development → cardiac failure in old age
• Sometimes collaterals themselves develop atherosclerosis → makes things worse

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📌 SECTION 8: MYOCARDIAL INFARCTION

What happens immediately after occlusion:

1. Blood flow ceases distal to the blockage
2. Small collateral blood trickles in → area overfills with stagnant blood
3. Muscle uses last O₂ → hemoglobin becomes fully deoxygenated → tissue turns bluish-brown
4. Blood vessels become highly permeable → leak fluid → local edema
5. Cardiac cells swell (failed cellular metabolism)
6. Within a few hours → cell death

O₂ thresholds:

⚠️ Subendocardial Infarction - Why Subendocardium Dies First:

• Subendocardial muscle has:
  1. Higher O₂ consumption than epicardial muscle
  2. Blood supply maximally compressed during systole
• So ANY reduction in coronary flow hits subendocardium first
• Infarction starts subendocardially and then spreads outward toward epicardium over time
• This is why early treatment (within minutes) can limit infarct to the subendocardium (NSTEMI) instead of full-thickness (STEMI)

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📌 SECTION 9: CAUSES OF DEATH AFTER ACUTE CORONARY OCCLUSION

1. 💀 Decreased Cardiac Output (Cardiogenic Shock)

• Infarcted muscle cannot contract
• During systole, normal muscle contracts but dead/nonfunctional muscle bulges OUTWARD (paradoxical motion) due to high intraventricular pressure
• This wastes pumping force → CO drops more than expected from amount of muscle lost

Normal muscle contracts → ↑ intraventricular pressure → 
Dead muscle bulges OUT → pressure energy is wasted → 
Net pumping reduced disproportionately

• Cardiogenic shock = CO too low for peripheral tissue survival
• Occurs when >40% of LV is infarcted
• Mortality: 40-50% even with treatment

2. 💀 Pulmonary Edema (Blood Damming)

• Heart fails to pump forward → blood dams up in pulmonary veins
• Pulmonary capillary pressure rises above plasma colloid osmotic pressure
• Fluid transudes into lung interstitium and alveoli → pulmonary edema
• Impairs gas exchange → hypoxia → death

3. 💀 Ventricular Fibrillation (MOST COMMON cause of sudden death post-MI)

• First 10 minutes after infarction (primary fibrillation)
• Short relative safety period
• 1 hour later, lasting several hours (secondary fibrillation)
• Can also occur days later (less common)

4. 💀 Rupture of the Heart Wall

• NOT immediate - occurs 3-7 days after infarction
• Dead muscle fibers begin to degenerate → wall becomes thin and weak
• Dead muscle bulges outward more with each beat → progressive systolic stretch
• Eventually wall ruptures → blood fills pericardial space → cardiac tamponade → rapid death
• Monitored by: Echo / MRI / CT (looking for progressive systolic stretch)
• When RV ruptures → blood in pericardium → compresses heart → blocks right atrial filling → sudden death

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📌 SECTION 10: STAGES OF RECOVERY FROM ACUTE MI

Acute Zone Structure (Size Dependent):

• Little or no permanent muscle death
• Part of muscle temporarily nonfunctional (stunned) → recovers

[CENTER]: Complete blood flow cessation → dies within 1-3 hours

[MIDDLE]: Nonfunctional zone → no contraction, no impulse conduction
           (reversible if blood flow restored promptly)

[OUTER]: Still contracting but WEAKLY → mild ischemia, borderline viable

Scar Formation:

• Macrophages/phagocytes invade and remove dead tissue
• Replaced by fibrous scar tissue (not muscle)
• Scar contracts → no longer bulges outward passively → partially restores mechanical efficiency

⭐ Coronary Steal Syndrome:

• During recovery, if patient exercises → normal muscle vasodilates greatly
• Blood preferentially flows through normal muscle vessels (lower resistance)
• Flow through anastomotic channels to ischemic zone decreases (stolen)
• Ischemic zone gets even LESS blood during activity than at rest
• This is why: ABSOLUTE REST is mandatory in the acute phase of MI

Physical Activity Post-MI:

• Acute phase: Absolute rest - reduces workload, prevents coronary steal
• After clinical stabilization: Prescribed aerobic exercise is beneficial
• Benefits of exercise training post-MI:
  • ↑ Coronary endothelial function
  • ↓ Inflammation
  • ↑ Contractile function of surviving cardiomyocytes
  • Partial recovery of cardiac reserve

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📌 SECTION 11: HEART FUNCTION AFTER RECOVERY FROM MI

• Occasionally recovers almost fully (rare)
• More often: permanently reduced pumping capacity
• Normal cardiac reserve = 300-400% above resting needs
• Even when reserve is reduced to 100% → most daily activities still possible
• Inability to increase CO during strenuous exercise is the typical deficit
• Cardiac rehabilitation (exercise) can partially restore reserve

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📌 SECTION 12: CARDIAC PAIN IN CORONARY HEART DISEASE

Mechanism of Ischemic Cardiac Pain:

• Ischemia → muscle releases acidic metabolites (lactic acid) + pain-promoting substances: histamine, kinins, proteolytic enzymes
• Slowly moving/stagnant blood fails to clear these
• High concentrations → stimulate pain nerve endings in cardiac muscle
• Pain signals travel via afferent fibers to spinal cord

Angina Pectoris:

• Definition: chest pain due to transient cardiac ischemia without cell death
• Occurs when metabolic demand > available coronary supply
• Location: Beneath the upper sternum (precordial area)
• Referred pain locations (embryological basis):
  • Left arm and left shoulder (most classic)
  • Neck
  • Side of face
  • Why: During embryonic development, heart originates in the neck → heart + left arm share the same spinal cord pain segments

• Exercise (↑ heart metabolism)
• Emotional stress (sympathetic vasoconstriction + ↑ metabolism)
• Cold temperatures (↑ cardiac workload via vasoconstriction + shivering)
• Full stomach (↑ venous return → ↑ cardiac work)
• Pain character: hot, pressing, constricting; severe enough that patient stops all activity
• Duration: usually a few minutes; constant pain = severe ischemia

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📌 SECTION 13: TREATMENT OF CORONARY ARTERY DISEASE

💊 Drug Treatment for Angina

🔪 Aortic-Coronary Bypass Surgery (CABG)

• Indication: discrete atherosclerotic blockages at a few points; vessels otherwise normal
• Procedure: saphenous vein (leg) or internal mammary artery graft from aortic root to coronary artery distal to the blockage
• Usually 1-5 grafts per patient
• Results: anginal pain relieved in most patients; normal life expectancy if heart not severely pre-damaged

🎈 Coronary Angioplasty + Stenting (PCI)

• Indication: partial occlusion before total occlusion develops (also used for acute total occlusions)
• Procedure: 1mm balloon-tipped catheter inserted → guided to blockage → balloon inflated at high pressure → vessel lumen widened
• Results: flow increases 3-4× immediately; >75% relieved of ischemic symptoms for at least several years
• BUT: many still eventually need CABG
• Stent: Stainless steel mesh tube placed inside vessel after balloon dilation:
  • Keeps vessel open mechanically
  • Prevents vessel from re-collapsing (elastic recoil)
  • Reduces restenosis rates
  • Drug-eluting stents: coated with anti-proliferative drugs to reduce scar tissue re-stenosis

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📌 SECTION 14: MASTER SUMMARY TABLE

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📌 SECTION 15: CONCEPT DIAGRAM - CORONARY FLOW CONTROL LOGIC

↑ CARDIAC WORK (exercise, stress)
          ↓
   ↑ O₂ Demand → ↓ local O₂ tension
          ↓
  ATP → ADP → AMP → ADENOSINE + other vasodilators
  (+ K⁺, H⁺, CO₂, NO, prostaglandins)
          ↓
   Coronary arteriolar DILATION
          ↓
   ↑ Coronary blood flow (up to 3-4× resting)
          ↓
   O₂ supply matches demand → metabolism restored

CORONARY OCCLUSION TIMELINE:
0 sec   → Flow stops; collaterals start dilating
Minutes → <50% needed flow via collaterals
30 min  → Adenine base depleted → cells begin to die irreversibly
Hours   → Center of infarct dead; subendocardium affected first
8-24h   → Collateral diameters barely changed
Day 2-3 → Collateral flow doubles
~1 month → Near-normal collateral flow
3-7 days → Necrotic wall thin → RUPTURE RISK PEAK
Weeks   → Scar tissue replaces dead muscle

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🩸 ROBBINS & COTRAN — CHAPTER 11

THE BLOOD VESSELS (Pathologic Basis of Disease, 10th Ed.)

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🔷 PART 1: VASCULAR STRUCTURE & FUNCTION (Normal)

═══════════════════════════════════

Wall Architecture

Layers are better defined in arteries than veins

Vessel Type Specializations

Rule: Atherosclerosis → elastic + muscular arteries; Hypertension → small muscular arteries + arterioles; Vasculitis → caliber-specific

Vasa Vasorum

• Small vessels that supply the walls of large vessels (aorta, large arteries)
• When occluded/disrupted → medial ischemia → aneurysm or dissection

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🔵 Endothelial Cell (EC) Biology

• Triggered by: cytokines (TNF, IL-1), bacterial products (LPS), turbulent/disturbed flow, lipid products (oxidized LDL), AGEs (in diabetes), viruses, complement, hypoxia
• Activated ECs: ↑ adhesion molecules, MHC molecules, cytokines, chemokines, growth factors, vasoactive/procoagulant factors

• = Alteration of EC phenotype toward proinflammatory + prothrombogenic state
• Underlies virtually all vascular disease

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🔵 Smooth Muscle Cell (SMC) Biology

• Two phenotypes:

• SMCs can be recruited from circulating bone marrow precursors and transition between phenotypes
• SMC proliferation and matrix synthesis → intimal thickening (fundamental response to injury)

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🔴 Intimal Thickening: Stereotyped Vascular Injury Response

• The universal vessel wall response to any injury
• Sequence: EC injury/dysfunction → SMC proliferation and migration from media to intima → ECM deposition → neointima formation
• If EC is intact → neointima formation with smooth surface; SMC secretion of factors perpetuates the process
• If EC is lost → platelet adherence → thrombus → organization → fibroblast/SMC ingrowth → lesion
• This process underlies: atherosclerosis, hypertensive changes, post-angioplasty restenosis, graft failure

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🔷 PART 2: HYPERTENSIVE VASCULAR DISEASE

═══════════════════════════════════

Definitions

• Hypertension: systolic ≥130 mm Hg and/or diastolic ≥80 mm Hg (current guidelines)
• Affects ~30-45% of adults in developed countries
• Primary (essential) hypertension: ~95% of cases; complex polygenic + environmental
• Secondary hypertension: ~5%; identifiable cause

Mechanisms of Secondary Hypertension

Mechanisms of Essential Hypertension

• RAAS dysregulation - abnormal salt handling, ↑ Ang II tone
• SNS hyperactivity
• Reduced nephron number (fewer nephrons from birth or injury → ↑ Na retention)
• Genetic factors - multiple polymorphisms in: Na⁺ transporters, RAAS genes, adrenergic receptors
• Environmental - high salt diet, obesity, sedentary lifestyle, stress
• Inflammation - immune cells (especially T cells) infiltrate kidney → promote Na retention

Vascular Pathology in Hypertension

• Seen in: benign hypertension + diabetes
• Mechanism: plasma protein leakage into walls + excessive SMC-produced matrix
• Morphology: homogeneous, pink (hyaline) thickening of arteriolar walls → narrowed lumen
• Target organs: kidneys (most important), retina, brain

• Seen in: malignant hypertension (acute severe HTN, diastolic >120 mm Hg)
• Morphology: "onion-skin" concentric laminated layers of SMCs + thickened BM → severe luminal narrowing
• Can progress to: fibrinoid necrosis → necrotizing arteriolitis → small vessel rupture → hemorrhage
• Clinical: papilledema, encephalopathy, renal failure (rapidly progressive)

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🔷 PART 3: ARTERIOSCLEROSIS

═══════════════════════════════════

• = Generic term for arterial wall thickening and loss of elasticity ("hardening of the arteries")
• Three patterns:

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🔷 PART 4: ATHEROSCLEROSIS ⭐ (Most Important)

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Definition

• Intimal-based lesion composed of a fibrous cap + atheromatous (lipid) core
• Affects elastic arteries (aorta, carotids, iliacs) and large/medium muscular arteries (coronaries, renals, lower extremity arteries)
• #1 cause of morbidity + mortality in developed world

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Risk Factors

• Hyperlipidemia (especially ↑ LDL, ↓ HDL)
• Hypertension
• Cigarette smoking
• Diabetes mellitus

• Age (men >45 yrs; women >55 yrs post-menopause)
• Male sex
• Family history / genetics

• C-reactive protein (CRP) - marker of inflammation
• Homocysteine - causes EC injury
• Lipoprotein(a) - competes with plasminogen
• Metabolic syndrome (obesity + HTN + dyslipidemia + insulin resistance)
• Clonal hematopoiesis (TP53 mutations in blood cells → ↑ risk)
• Low socioeconomic status

• HDL (reverse cholesterol transport)
• Exercise
• Moderate alcohol consumption (modest effect)

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Pathogenesis: Response-to-Injury Hypothesis

Central concept: Atherosclerosis = chronic inflammatory response of the arterial wall to EC injury/dysfunction.

Step 1: ENDOTHELIAL INJURY/DYSFUNCTION
   ↓ (from: turbulent flow (especially at branch points),
      hyperlipidemia, HTN, smoking, homocysteine, immunologic)
   
Step 2: LIPOPROTEIN (LDL) ACCUMULATION IN INTIMA
   ↓ (oxidized LDL = oxLDL is the key pathogenic form)
   
Step 3: MONOCYTE RECRUITMENT + MACROPHAGE DIFFERENTIATION
   ↓ (via adhesion molecules on activated ECs: VCAM-1, ICAM-1)
   Macrophages phagocytose oxLDL via scavenger receptors
   → become FOAM CELLS (lipid-laden macrophages)
   → form "fatty streak" (earliest visible lesion)
   
Step 4: PLATELET ADHESION (if EC denuded)
   + T cell recruitment
   ↓
   
Step 5: SMC MIGRATION from media to intima
   (driven by: PDGF from platelets/macrophages/ECs, FGF, TGF-α)
   SMC phenotype switches: contractile → synthetic
   ↓
   
Step 6: ECM SYNTHESIS by SMCs
   (collagen, elastin, proteoglycans → fibrous cap formation)
   
Step 7: LIPID ACCUMULATION
   Extracellular lipid + foam cell debris → atheromatous necrotic core
   
Step 8: PLAQUE FORMATION = Fibrous cap + necrotic lipid core

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Morphology of Atherosclerosis

• Begins as early as childhood/adolescence
• Intimal collections of foam cells (lipid-laden macrophages) + T lymphocytes
• Flat to mildly elevated; yellow
• Not yet significant clinically
• Not all fatty streaks progress to plaques

• Fibrous cap: Dense ECM (collagen) + SMCs ± inflammatory cells
• Necrotic core: Lipid debris, foam cells, cholesterol crystals, calcification
• Shoulder regions: Most metabolically active; macrophage-rich
• Vasa vasorum: Can proliferate and invade the plaque base

• Creamy-yellow; patchy; irregular luminal surface
• Most severe in: abdominal aorta > coronary arteries > popliteal arteries > descending thoracic aorta > internal carotid arteries > vessels of circle of Willis

• Fibrous cap: SMCs, collagen, proteoglycans
• Underlying core: foam cells, extracellular lipid, cholesterol clefts, necrotic debris
• Calcification (dystrophic) in advanced lesions
• Neovascularization (new blood vessels grow into plaque from adventitia)

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Plaque Progression and Complications

• Dense fibrous cap, minimal lipid, little inflammation
• Produces symptoms by chronic, flow-limiting stenosis → stable angina, claudication
• Lesion must narrow lumen >70% (critical stenosis) to cause ischemia at rest

• Thin fibrous cap, large lipid core, many macrophages and foam cells, few SMCs, more inflammation
• Prone to ACUTE PLAQUE RUPTURE (most common cause of ACS/MI/stroke)
• MMPs (from macrophages) degrade fibrous cap collagen → weakening
• Thin caps + inflammation = danger

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Clinical Consequences of Atherosclerosis

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🔷 PART 5: ANEURYSMS AND DISSECTION

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Definitions

• Saccular: Focal outpouching involving only part of the circumference
• Fusiform: Circumferential, spindle-shaped dilation of the whole vessel

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Abdominal Aortic Aneurysm (AAA)

• Location: Below the renal arteries (infrarenal) - most common
• Size threshold for rupture risk: >5 cm diameter
• Cause: Atherosclerosis (>95%) → medial destruction by lipid/inflammation + ↓ elastin/collagen synthesis
• Risk factors: Age >60, male sex, smoking (major risk!), family history, HTN
• Morphology: Fusiform dilation of infrarenal aorta; luminal mural thrombus (atherosclerotic)
• Complications:
  • Rupture (catastrophic - mortality 50-80% even with surgery)
  • Thrombosis → downstream embolism/ischemia
  • Compression of adjacent structures (ureters, vertebrae, duodenum)
  • Atherosclerotic embolism
• Screening: Ultrasound for men aged 65-75 who ever smoked
• Variants:
  • Inflammatory AAA (5-10%): Dense peri-aortic fibrosis + inflammatory infiltrate; some associated with IgG4-related disease
  • Mycotic AAA: Bacterial/fungal seeding of aortic wall (Pseudomonas, Salmonella); hematogenous or from adjacent infection

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Thoracic Aortic Aneurysm (TAA)

• Cause: Cystic medial degeneration >> atherosclerosis
• Associations:
  • Marfan syndrome (FBN1 mutation → ↓ fibrillin-1 → ↑ TGF-β signaling → elastin breakdown)
  • Bicuspid aortic valve (associated structural ECM weakness of aortic root)
  • Hypertension (major accelerating factor)
  • Tertiary syphilis → endarteritis obliterans of vasa vasorum → medial ischemia → ascending aorta aneurysm (classically involves aortic root → aortic valve regurgitation)
• Morphology: Fusiform, usually ascending aorta; cystic medial change = loss of elastic fibers + SMC dropout + mucoid/cystic spaces
• Complications:
  • Aortic valve regurgitation (if involves aortic root)
  • Superior vena cava syndrome
  • Dysphagia, hoarseness, cough (compression of adjacent structures)
  • Rupture
  • Dissection

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Aortic Dissection

• Blood splits through the media (not just intima) creating a false lumen
• NOT the same as aneurysm - dissection can occur without prior aneurysm (though often coexists)
• Can also arise from rupture of vasa vasorum within media

• Hypertension (#1 precipitant - present in ~75%)
• Cystic medial degeneration (Marfan syndrome, bicuspid aortic valve, Ehlers-Danlos)
• Age 40-60 in HTN patients; younger in Marfan/connective tissue disorders
• Pregnancy (especially 3rd trimester - hormonal changes weaken aortic wall)
• Rare: iatrogenic (cardiac catheterization), trauma, cocaine use

• Entry tear usually in ascending aorta within 10 cm of aortic valve, or just distal to left subclavian origin
• False lumen (between inner 2/3 and outer 1/3 of media) fills with clotted blood
• Can propagate proximally and/or distally
• May re-enter lumen downstream (double-barrel aorta) or rupture outward

• Hemopericardium → cardiac tamponade (most deadly acute complication)
• Aortic valve insufficiency (disruption of leaflet support)
• MI (occlusion of coronary ostia)
• Stroke (occlusion of carotid ostia)
• Rupture into mediastinum/pleural cavity

• Mesenteric/renal ischemia
• Lower limb ischemia
• Rupture (less common acutely)

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🔷 PART 6: VASCULITIS

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Definition & Overview

• = Inflammation of vessel walls
• Manifestations depend on vascular bed involved
• Systemic: fever, myalgias, arthralgias, malaise + organ-specific features

Two Pathogenic Mechanisms:

1. Direct infectious invasion of vessel wall
2. Immune-mediated (most common):
   • Immune complex deposition
   • ANCA (antineutrophil cytoplasmic antibody)
   • Anti-EC antibodies + autoreactive T cells
   • Anti-GBM antibodies

⚠️ Must distinguish infectious vs. immune → immunosuppression helps immune, harms infectious

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Infectious Vasculitis

• Agents: Pseudomonas, Aspergillus, Mucor most common
• Via: local tissue spread from adjacent infection, or hematogenous
• Consequences: mycotic aneurysm formation, thrombosis → downstream infarction
• Example: bacterial meningitis → inflammation-induced thrombosis of meningeal vessels → brain infarction

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Noninfectious Vasculitis - Classification by Vessel Size

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🔴 LARGE VESSEL VASCULITIS

1. Giant Cell (Temporal) Arteritis

• Most common vasculitis in developed countries
• Age: Almost exclusively in people >50 years (peak 70-80s)
• Sex: Female >> male (2:1)
• Vessels: Temporal artery (classic), also ophthalmic, vertebral, internal carotid; less often aorta and its major branches

• Granulomatous inflammation triggered by unknown antigen in vessel wall
• Activated CD4⁺ T cells + macrophages → granuloma with giant cells
• IL-6 markedly elevated (correlates with disease activity; basis for IL-6 blockade therapy)

• Granulomatous inflammation of inner media → giant cells (Langhans and foreign-body type) clustered around fragmented internal elastic lamina
• Intimal thickening → luminal narrowing
• Skip lesions (not uniform along vessel)
• Late stage: fibrotic healing → "pipestem" artery

• Temporal headache (most classic)
• Tenderness and nodularity/thickening of temporal artery; absent pulse
• Jaw claudication (pain on chewing) - from ischemia of masseter
• Sudden irreversible blindness - most feared complication (from ophthalmic artery involvement)
• Fever, malaise, weight loss, elevated ESR/CRP
• Often associated with polymyalgia rheumatica (shoulder/hip girdle pain and stiffness in ~50% of GCA patients)
• ↑ IL-6

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2. Takayasu Arteritis ("Pulseless Disease")

• Age: <50 years (usually 20s-40s)
• Sex: Female >> male (9:1)
• Geographic predilection: Asia, Middle East, Latin America
• Vessels: Aorta + great branches (subclavian, renal, carotid, mesenteric, coronary)

• Granulomatous adventitial inflammation → progresses to severe fibrous thickening of aortic wall and branch ostia
• Gross: irregular intimal plaques; tree bark-like intima
• Late: progressive luminal narrowing of aortic branches

• Absent pulses in upper extremities (subclavian stenosis) → pulse difference between arms
• BP differential between arms >10 mm Hg
• Ocular disturbances, retinal hemorrhages (carotid/ophthalmic stenosis)
• Neurological symptoms (carotid stenosis)
• Hypertension (renal artery stenosis)
• Aortic regurgitation (if aortic root involved)
• Constitutional symptoms: fever, fatigue, weight loss, elevated ESR

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🟠 MEDIUM VESSEL VASCULITIS

3. Polyarteritis Nodosa (PAN)

• Affects medium-sized muscular arteries (renal, hepatic, coronary, mesenteric)
• Does NOT involve: pulmonary vessels, glomerular vessels
• No ANCA association
• Hepatitis B association in ~30% of cases (immune complex deposition)
• Can occur at any age; more common in young adults

• Segmental (not continuous), necrotizing inflammation affecting entire vessel wall
• Fibrinoid necrosis of wall + transmural inflammatory infiltrate
• Skip lesions (normal segments between diseased segments)
• Acute: fibrinoid necrosis + neutrophils
• Healing: fibrosis, obliteration, aneurysmal dilation at branch points (classic "beaded" pattern on angiography)

• Fever, weight loss, malaise
• Hypertension (renal involvement)
• Abdominal pain (mesenteric ischemia)
• Peripheral neuropathy (vasa nervorum involvement) - very common
• Myalgias, arthralgias
• Skin nodules, livedo reticularis, ulcers
• Renal involvement → hematuria, proteinuria, renal failure

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4. Kawasaki Disease (Mucocutaneous Lymph Node Syndrome)

• Age: Children <5 years (peak 6-24 months); rare in adults
• Ethnicity: Originally described in Japan; higher incidence in Asian populations
• Cause: Unknown; likely infectious trigger + immune dysregulation

• Acute: Necrotizing arteritis of coronary arteries → coronary artery aneurysms (in 15-25% untreated)
• Resembles PAN histologically in acute phase

1. Fever ≥5 days
2. Bilateral conjunctival injection (non-exudative)
3. Oral mucosa changes (strawberry tongue, lip cracking/erythema, pharyngeal erythema)
4. Rash (polymorphous exanthem)
5. Extremity changes (edema, erythema of palms/soles → desquamation)
6. Cervical lymphadenopathy (often unilateral, ≥1.5 cm)

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🟡 SMALL VESSEL VASCULITIS

ANCA-Associated Vasculitides (AAV)

ANCA = antineutrophil cytoplasmic antibodies

• c-ANCA (PR3-ANCA): anti-proteinase-3; pattern = cytoplasmic
• p-ANCA (MPO-ANCA): anti-myeloperoxidase; pattern = perinuclear

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5. Granulomatosis with Polyangiitis (GPA) (formerly Wegener)

• c-ANCA (PR3-ANCA) positive in ~90%
• Triad: upper respiratory tract + lower respiratory tract + kidneys
• Classic triad: Necrotizing granulomas of upper/lower RT + necrotizing vasculitis of small/medium vessels + focal necrotizing glomerulonephritis

• Saddle-nose deformity (nasal cartilage destruction)
• Chronic sinusitis, otitis media, epistaxis
• Oral/nasal ulcers with tissue destruction
• Pulmonary: nodules/cavities, hemoptysis, dyspnea
• Renal: rapidly progressive glomerulonephritis (RPGN) → hematuria, proteinuria, renal failure
• Eyes: conjunctivitis, proptosis, orbital pseudotumor (granuloma)

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6. Eosinophilic Granulomatosis with Polyangiitis (EGPA) (formerly Churg-Strauss)

• p-ANCA (MPO-ANCA) positive in ~40%
• Classic triad: Asthma + eosinophilia + systemic vasculitis
• Mainly upper/lower respiratory tract involvement initially → then systemic

• Asthma (almost always present - hallmark)
• Peripheral + tissue eosinophilia
• Allergic rhinitis, nasal polyps
• Cardiac involvement (eosinophilic myocarditis/endocarditis) - major cause of death
• Peripheral neuropathy (mononeuritis multiplex)
• Skin nodules, purpura

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7. Microscopic Polyangiitis (MPA)

• p-ANCA (MPO-ANCA) positive in ~70%
• Affects: small vessels (capillaries, venules, arterioles); also medium arteries sometimes
• No granulomas (unlike GPA and EGPA)
• Pauci-immune (no/minimal immune complex deposition)

• Necrotizing glomerulonephritis (RPGN) - most common cause of death
• Pulmonary capillaritis → diffuse alveolar hemorrhage
• Skin purpura
• Peripheral neuropathy
• Abdominal pain, GI bleeding

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Immune Complex-Associated Small Vessel Vasculitis

• Most common vasculitis in children
• IgA immune complex deposition in small vessel walls
• Classic tetrad:
  1. Purpura (non-thrombocytopenic; palpable; lower extremities/buttocks)
  2. Arthritis/arthralgias
  3. Abdominal pain/GI bleeding (bowel ischemia)
  4. Renal disease (IgA nephropathy-like; hematuria ± nephrotic syndrome)
• Often follows upper respiratory infection (IgA-triggering)
• Treatment: supportive; steroids for severe cases

• Immune complex deposition with cryoglobulins (immunoglobulins that precipitate at cold temperatures)
• Most commonly: Hepatitis C infection (mixed cryoglobulinemia type II/III)
• Clinical: purpura, arthralgia, weakness, peripheral neuropathy, glomerulonephritis
• Treatment: treat underlying HCV infection; steroids/rituximab for severe cases

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Anti-GBM Antibody Disease (Goodpasture Syndrome)

• Anti-GBM antibodies cross-react with pulmonary alveolar BM
• Glomerulonephritis (RPGN) + pulmonary hemorrhage
• Treated with plasma exchange + immunosuppression

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🔷 PART 7: DISORDERS OF BLOOD VESSEL HYPERREACTIVITY

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Raynaud Phenomenon

• Exaggerated vasoconstriction of arteries/arterioles in response to cold or emotion
• Affects: fingers/toes most commonly; also nose, earlobes, lips
• Classic color change: Red (proximal vasodilation) → White (vasoconstriction) → Blue (distal cyanosis) ("red-white-blue" from proximal to distal)

⚠️ Raynaud phenomenon may be the FIRST manifestation of immune-mediated vasculitis. New onset → evaluate for underlying disease. ~10% will eventually manifest a systemic disorder.

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Myocardial Vessel Vasospasm

• Excessive constriction of coronary arteries/arterioles
• Can produce variant (Prinzmetal) angina - rest pain, ST elevation, no fixed stenosis
• Triggers: cold, stress, cocaine, alpha-adrenergic agonists
• More common in arteries with underlying atherosclerosis (even mild plaques)
• Can precipitate MI and sudden death
• Treatment: calcium channel blockers + nitrates (avoid beta-blockers)

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🔷 PART 8: VEINS AND LYMPHATICS

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Varicose Veins

• = Abnormally dilated, tortuous veins caused by chronically increased intraluminal pressure
• Most common sites: lower extremity superficial veins (great + small saphenous system)
• Prevalence: ~15% of adults

• Prolonged standing (occupation - surgeons, teachers, nurses, etc.)
• Pregnancy (↑ blood volume + venous pressure + hormonal relaxation of vein walls)
• Obesity
• Hereditary weakness of venous walls
• Prior DVT (damages valves → valve incompetence → secondary varicosities)

• Venous valve incompetence (incompetent valves) → blood refluxes downward → ↑ pressure → venous dilation → further valve incompetence (vicious cycle)

• Tortuous, dilated, elongated veins
• Irregular wall thickening (hypertrophied smooth muscle in areas of dilation; atrophied in others)
• Intimal fibrosis
• Calcified thrombi ("phleboliths")

• Stasis → impaired venous drainage → chronic venous insufficiency
• Varicose ulcers (especially medial malleolus) - from tissue hypoxia/ischemia
• Poor healing of wounds
• Thrombosis of superficial varices (less dangerous than DVT)
• Variceal hemorrhage (if significant trauma)
• Cosmetic concerns

• Esophageal varices: Portal hypertension → portosystemic shunting through coronary vein → gastroesophageal veins; catastrophic hemorrhage risk
• Hemorrhoidal veins: Engorgement of the hemorrhoidal plexus; symptomatic hemorrhoids
• Varicocele: Dilation of pampiniform plexus of spermatic vein (left > right); associated with male infertility

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Thrombophlebitis and Phlebothrombosis

• Thrombophlebitis: Venous thrombosis in setting of primary inflammation (infectious or sterile)
• Phlebothrombosis: Venous thrombosis without primary inflammation (Virchow's triad)
• In practice, these terms are used interchangeably because they co-exist

• Deep veins of legs (90% of DVT): calf, popliteal, femoral, iliac
• Mesenteric veins (hypercoagulable states)
• Hepatic veins (Budd-Chiari syndrome)
• Dural venous sinuses (intracranial thrombosis)
• Portal vein

1. Stasis - immobility, cardiac failure, pregnancy, varicosities
2. Hypercoagulability - factor V Leiden, antiphospholipid syndrome, cancer, OCP, nephrotic syndrome
3. Endothelial injury - trauma, surgery, indwelling catheters

• Recurrent venous thromboses at unusual/migratory sites
• Association with occult visceral carcinoma (pancreatic, lung, gastric, colon)
• Tumor-secreted procoagulant factors

• Pulmonary embolism (major cause of sudden death)
• Post-thrombotic syndrome (valve damage → chronic venous insufficiency, ulcers)
• Phlegmasia cerulea dolens (massive proximal DVT → entire limb cyanosis/pain)

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Superior Vena Cava (SVC) Syndrome

• Cause: Compression or invasion of SVC
• Most common cause: Bronchogenic carcinoma (right upper lobe) or lymphoma
• Clinical:
  • Progressive facial/neck/arm swelling (pitting edema) and cyanosis
  • Edema of upper extremities and neck ("collar of stokes")
  • Dilated superficial veins on chest wall (collateral drainage)
  • Headache, visual disturbances (↑ cerebral venous pressure)
  • Potentially fatal if cerebral edema develops

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Inferior Vena Cava (IVC) Syndrome

• Cause: Compression by adjacent tumor, hepatic abscess, retroperitoneal fibrosis; thrombosis
• Common associations: hepatocellular carcinoma (invades IVC), renal cell carcinoma (tumor thrombus extends into IVC)
• Clinical:
  • Leg edema
  • Distension of superficial collateral vessels of the abdominal wall
  • Massive proteinuria (if renal veins obstructed)

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Lymphangitis and Lymphedema

• Acute: Bacterial infection → spreads along lymphatics → red streaks under skin ("blood poisoning" - misnomer); most commonly group A Streptococcus
• Can lead to bacteremia/septicemia
• Regional lymph nodes enlarge and become painful (reactive lymphadenopathy)

• Accumulation of lymph due to lymphatic obstruction → protein-rich edema
• Primary (congenital):
  • Milroy disease: congenital hereditary lymphedema (lower extremities; VEGFR3 mutation)
  • Simple primary lymphedema (idiopathic onset in 2nd-3rd decade)
• Secondary (most common):
  • Lymph node dissection (post-mastectomy → arm lymphedema "brawny arm")
  • Radiation-induced lymphatic fibrosis
  • Filariasis (Wuchereria bancrofti) - most common cause worldwide → massive scrotal/lower extremity lymphedema = elephantiasis
  • Tumor obstruction of lymphatics
  • Recurrent infections
• Complications of chronic lymphedema:
  • Protein-rich edema → fibrosis → "brawny" (non-pitting) induration
  • Risk of lymphangiosarcoma (Stewart-Treves syndrome after mastectomy)

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🔷 PART 9: VASCULAR TUMORS

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Classification

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Benign Tumors and Tumor-like Conditions

Vascular Ectasias (Telangiectasias)

• = Localized permanent dilation of pre-existing vessels (NOT true tumors)
• Types:
  • Nevus flammeus (port-wine stain): Flat, purplish lesion on face/neck; irregular superficial vessels; grows with child; does NOT involute; may be associated with Sturge-Weber syndrome (if V1 distribution → leptomeningeal angioma → epilepsy/intellectual disability)
  • Spider telangiectasia (spider angioma): Central feeding arteriole with radiating small vessels; seen in cirrhosis (↑ estrogen) and pregnancy; blanches on pressure; refills from center
  • Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu): AD; ENG/ACVRL1 mutations (TGF-β pathway); telangiectasias in mucous membranes, GI tract, skin, lungs → recurrent epistaxis, GI bleeding, AV malformations

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Hemangiomas

• Most common benign vascular tumors; occur in all ages
• Most frequently in skin and soft tissues

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Lymphangiomas

• Benign tumors of lymphatic vessels
• Simple (capillary) lymphangioma: Occur in head/neck of children; small vessels lined by EC
• Cavernous lymphangioma (cystic hygroma): Dilated lymphatic spaces; most common in neck; associated with Turner syndrome (45,X) and Down syndrome

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Glomus Tumor (Glomangioma)

• Benign, extremely painful tumor arising from modified SMCs of glomus bodies (arteriovenous shunts in skin)
• Most common in subungual region of fingers (under fingernails)
• Also: distal extremities
• Morphology: small; nests/organoids of round uniform cells surrounding vascular spaces
• Treatment: surgical excision → curative; exquisitely painful on pressure

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Bacillary Angiomatosis

• Vascular proliferation caused by Bartonella henselae or B. quintana infection
• Seen almost exclusively in HIV/AIDS patients and other immunocompromised
• NOT a true neoplasm - it is an infectious vascular proliferation
• Morphology: looks like Kaposi sarcoma; lobular proliferation of plump (epithelioid) ECs; neutrophilic infiltrate; clumps of bacilli (Warthin-Starry silver stain)
• Treatment: Erythromycin (antibiotic)

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Intermediate (Borderline) Tumors

Kaposi Sarcoma (KS)

• Vascular tumor caused by HHV-8 (Human Herpesvirus-8/Kaposi Sarcoma Herpesvirus)
• Exists in several clinical forms

• HHV-8 infects ECs → immortalization
• CD4 T-cell immunosuppression → allows HHV-8 replication
• HHV-8 proteins: LANA-1 (inhibits p53 + RB), vIL-6 (viral homologue), vCCL-2/3 (viral chemokines), vCyclin (CDK6 activator → cell proliferation)
• Not a true cancer - it is a reactive/proliferative lesion driven by HHV-8

• Patch stage: Dilated, irregular, angular vascular channels in dermis; few atypical ECs; barely visible
• Plaque stage: More evident; confluent vascular channels lined by spindle cells
• Nodular stage: Cellular; sheets of spindle-shaped ECs; slit-like vascular channels; extravasated RBCs (hemosiderin deposits); mitoses

• Skin: painless purple/brown macules → nodules; lower extremities → disseminates
• AIDS-KS: oral mucosa, GI tract, lungs, lymph nodes → severe complications
• Treatment: for AIDS-KS → HAART (antiretroviral therapy) can induce regression; localized → radiation; systemic → chemotherapy (liposomal doxorubicin, paclitaxel)

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Hemangioendothelioma

• Intermediate malignant potential (between hemangioma and angiosarcoma)
• Epithelioid hemangioendothelioma: liver, lung; short spindle to rounded EC tumor cells; variable behavior
• Treatment: wide local excision; some require chemo

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Malignant Tumors

Angiosarcoma (Hemangiosarcoma)

• Malignant tumor of vascular endothelial cells
• Can arise in any tissue but most common in: skin, soft tissue, breast, liver

• Post-mastectomy lymphedema → cutaneous angiosarcoma of arm (Stewart-Treves syndrome)
• Thorotrast (old radiologic contrast - thorium dioxide) → hepatic angiosarcoma
• Vinyl chloride → hepatic angiosarcoma
• Arsenic → hepatic angiosarcoma
• Chronic lymphedema → cutaneous angiosarcoma
• Radiation-associated (secondary to prior radiotherapy)

• Poorly defined margins; gray-white lesions ± hemorrhage
• Histology: variable - well-differentiated (distinct vascular channels with atypical ECs) to poorly differentiated (solid sheets, few vascular spaces)
• IHC markers: CD31, CD34, ERG (endothelial markers)
• Aggressive: local invasion + hematogenous spread

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🔷 PART 10: PATHOLOGY OF VASCULAR INTERVENTION

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Endovascular Stenting (Angioplasty + Stent)

• Balloon catheter inflates → stretches/compresses plaque → opens lumen
• Stent (metal mesh) deployed → mechanically maintains luminal patency

• Elastic recoil of vessel wall immediately after balloon deflation
• Stent prevents this mechanical recoil

• Mechanism: Vascular injury during angioplasty → intimal response (smooth muscle proliferation + ECM) → neointimal hyperplasia → luminal renarrowing
• Not atherosclerosis re-accumulating; it is a wound-healing response

• Coated with anti-proliferative drugs (paclitaxel, sirolimus/rapamycin, everolimus)
• Drugs inhibit SMC proliferation → markedly reduce restenosis (<10% at 1 year)
• BUT: DES delay endothelialization → risk of late stent thrombosis (months to years) if antiplatelet therapy stopped → dual antiplatelet therapy (aspirin + P2Y12 inhibitor) required for 6-12 months minimum

• Bare metal: early (hours to days) from incomplete stent apposition or platelet activation
• Drug-eluting: late/very late (months to years) due to impaired re-endothelialization

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Vascular Replacement (Bypass Grafts)

• Autologous vein grafts (saphenous vein, internal mammary artery) - best long-term patency
• Prosthetic grafts (Dacron, PTFE/Gore-Tex) - used when autologous vessels unavailable

• When vein placed in arterial position → exposed to higher pressures and flow
• Develops: intimal hyperplasia, medial hypertrophy → eventually becomes "arterialized"
• Long-term: atherosclerosis develops in graft, especially at anastomoses

• Thrombosis (especially small-diameter grafts)
• Graft infection → often requires graft removal (life-threatening)
• Anastomotic pseudoaneurysm (at suture line between graft and natural artery)
• Graft-to-bowel fistula (aorto-enteric; rare but fatal)

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📋 MASTER SUMMARY TABLE

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