Atherosclerosis Revision Sheet

1. 📌 Essentials

• A disease characterized by lipid deposits (atheromas) in medium-large arteries' intima.
• Main risk factors: hypercholesterolemia, hypertension, smoking, diabetes, age.
• Initiates with endothelial dysfunction precipitated by risk factors.
• LDL cholesterol infiltration and oxidation trigger early lesion development.
• Foam cells derive from monocytes that migrate and transform in the vessel wall.
• Plaques consist of a lipid core, fibrous cap, and cellular components.
• Plaque stability depends on collagen content and lipid richness.
• Cap rupture leads to thrombus formation, causing ischemia or infarction.
• Symptoms are often asymptomatic until >70% arterial narrowing.
• Affected arteries: coronary, carotid, lower limb arteries.

2. 🧩 Key Structures & Components

• Endothelial cells — regulate vascular permeability; initial site of dysfunction.
• LDL cholesterol — deposits in arterial wall, oxidizes contributing to atherogenesis.
• Monocytes/Macrophages — attracted to early lesion, become foam cells.
• Foam cells — lipid-laden macrophages; main component of fatty streaks.
• Vascular smooth muscle cells (VSMC) — migrate inward, produce collagen and extracellular matrix (ECM).
• Fibrous cap — collagen-rich layer covering the plaque, maintaining stability.
• Lipid core — necrotic debris, extracellular lipids, foam cells.
• Thrombus — formed after cap rupture, causes occlusion.

3. 🔬 Functions, Mechanisms & Relationships

• Risk factors (hypercholesterolemia, hypertension) cause endothelial dysfunction.
• Endothelial damage increases permeability, allowing LDL infiltration.
• LDL oxidation triggers immune response: monocytes migrate and turn into foam cells.
• Accumulating foam cells secrete cytokines, recruiting more immune cells.
• VSMCs migrate from media to intima, produce collagen, forming a protective fibrous cap.
• Stable plaques are collagen-rich; unstable are lipid-rich prone to rupture.
• Rupture exposes thrombogenic material, activating clotting cascade.
• Thrombus formation can cause partial or complete arterial occlusion.
• Progressive plaque growth leads to luminal narrowing, impairing blood flow.

4. 🗂️ Hierarchical Diagram (ASCII)

Atherosclerosis
 ├─ Initiation
 │    ├─ Endothelial dysfunction
 │    └─ LDL oxidation
 ├─ Early lesion
 │    ├─ Monocyte recruitment
 │    └─ Foam cell formation (fatty streak)
 ├─ Plaque development
 │    ├─ Foam cell accumulation
 │    ├─ VSMC migration and collagen production
 │    └─ Formation of fibrous plaque
 │        ├─ Lipid core
 │        └─ Fibrous cap
 └─ Plaque complication
      ├─ Cap rupture / fissure
      └─ Thrombus formation → occlusion

5. ⚠️ High-Yield Pitfalls & Confusions

• Confusing fatty streaks (early) with advanced fibrous plaques.
• Overlooking the distinction between stable and unstable plaques.
• Misinterpreting thin-cap fibroatheromas (vulnerable plaques) as stable.
• Mistaking cap rupture for simple plaque erosion.
• Assuming all plaques cause symptoms; many remain asymptomatic.
• Believing LDL oxidation occurs only in plasma, ignoring sub-endothelial space.
• Confusing causes of ischemia: plaque rupture vs. superimposed thrombosis.
• Underestimating the role of VSMCs in plaque stability.

6. ✅ Final Exam Checklist

• Know the stages of atherogenesis: initiation, fatty streak, fibrous plaque, complicated plaque.
• Identify the key cellular players: endothelial cells, monocytes, foam cells, VSMCs.
• Understand plaque composition: lipid core, fibrous cap, cellular elements.
• Differentiate between stable and vulnerable plaques.
• Recognize the pathological role of LDL cholesterol and oxidized LDL.
• Be familiar with common arteries affected: coronary, carotid, limb arteries.
• Comprehend the clinical manifestations based on artery and plaque stability.
• Know risk factor thresholds: LDL >160 mg/dl, BP ≥140/90 mmHg, fasting glucose >110 mg/dl.
• Understand the consequences of plaque rupture: thrombosis, ischemia, infarction.
• Recall symptoms: asymptomatic until significant stenosis; then angina, MI, stroke, claudication.
• Associate risk factors with development and progression of atherosclerosis.
• Be aware of the importance of plaque stability in clinical outcomes.
• Link pathophysiological processes to clinical symptoms and management.

End of Revision Sheet