Study guide: Understanding Atherosclerosis Formation and Risks

Atherosclerosis Revision Sheet

1. 📌 Essentials (Key Facts)

• Atherosclerosis = formation of fatty plaques (atheromas) in medium-large arteries.
• Deposits are mainly LDL cholesterol beneath the endothelium.
• Lesions start as fatty streaks in ages 10-20; symptomatic disease occurs after 35-40 years.
• Major risk factors: high LDL, hypertension, smoking, diabetes, age, obesity.
• Pathogenesis involves endothelial dysfunction, LDL oxidation, foam cell formation, and fibrous cap development.
• Plaques are classified as stable (collagen-rich) and unstable (lipid-rich).
• Critical stenosis causing symptoms: >70-75% narrowing.
• Plaque rupture exposes necrotic core, causing thrombosis and potential occlusion.
• Clinical syndromes: angina, MI, stroke, claudication, gangrene.
• Atheromatous deposits lead to ischemia in heart, brain, lower limbs.

2. 🧩 Key Structures & Components

• Endothelium — lines arteries, initial site of dysfunction.
• LDL cholesterol — main lipoprotein involved in plaque formation.
• Foam cells — macrophages laden with oxidized LDL, form fatty streaks.
• Vascular smooth muscle cells (VSMC) — migrate and produce collagen in fibrous cap.
• Fibrous cap — collagen-rich layer over necrotic core, stabilizes plaque.
• Lipid/necrotic core — consists of dead foam cells, cholesterol crystals, cellular debris.
• Plaque types — stable vs unstable based on composition.
• Thrombus — clot formed upon cap rupture.

3. 🔬 Functions, Mechanisms & Relationships

• Endothelial dysfunction allows LDL influx and oxidation beneath endothelium.
• Oxidized LDL attracts monocytes, which transform into foam cells.
• Foam cells accumulate into fatty streaks, the earliest lesion.
• VSMCs migrate from media into intima, producing collagen and forming fibrous cap.
• Plaque growth involves lipid accumulation, necrosis, and VSMC proliferation.
• Plaque rupture exposes necrotic core, activates clotting cascade, forming thrombus.
• Stable plaques retain collagen, are less prone to rupture; unstable plaques have large lipid cores.
• Critical stenosis (>70%) impairs blood flow, causing ischemic symptoms.
• Plaque instability leads to acute events: MI, stroke, gangrene.

4. Comparative Table: Stable vs Unstable Plaques

5. 🗂️ Hierarchical Diagram

Atherosclerosis
 ├─ Risk Factors
 │    ├─ High LDL
 │    ├─ Hypertension
 │    ├─ Smoking
 │    └─ Diabetes
 ├─ Pathogenesis
 │    ├─ Endothelial dysfunction
 │    ├─ LDL infiltration & oxidation
 │    ├─ Monocyte recruitment
 │    ├─ Foam cell formation
 │    ├─ Fatty streak development
 │    ├─ VSMC migration & collagen synthesis
 │    └─ Fibrous cap formation
 ├─ Plaque Evolution
 │    ├─ Stable plaques
 │    └─ Unstable plaques
 ├─ Complications
 │    ├─ Cap rupture
 │    └─ Thrombus formation
 └─ Clinical Outcomes
      ├─ Ischemia
      ├─ MI
      ├─ Stroke
      └─ Gangrene

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing fatty streaks with advanced plaques; fatty streaks are benign.
• Assuming all plaques cause symptoms; many are silent until critical stenosis.
• Overlooking the difference between stable and unstable plaques—stability depends on collagen vs lipid content.
• Misidentifying the role of foam cells—they are key in early lesion formation.
• Ignoring that plaque rupture is the main trigger for acute events.
• Thinking hypertension and hyperglycemia are the root causes; they are risk factors, not causes per se.
• Confusing clinical syndromes: angina vs MI, TIA vs stroke.
• Underestimating the importance of plaque composition in prognosis.

7. ✅ Final Exam Checklist

• Define atherosclerosis and identify its main features.
• List significant risk factors and their cutoff values.
• Describe stages of atherogenesis: initiation, fatty streak, fibrous plaque, complications.
• Explain the differences between stable and unstable plaques.
• Recognize histological features: foam cells, fibrous cap, necrotic core.
• Know the critical stenosis percentage for symptoms (>70-75%).
• Understand how plaque rupture leads to thrombosis.
• Match clinical syndromes to affected arteries: coronary, cerebral, limb.
• Recall key organs involved and their clinical manifestations.
• Explain the role of LDL cholesterol levels (>160 mg/dl) in risk.
• Identify the typical age range for disease onset.
• Recognize the importance of hypertension (≥140/90 mmHg).
• Understand that atherosclerosis causes ischemia, infarction, and organ damage.
• Know that prevention targets control of cholesterol, BP, smoking cessation, and diabetes management.
• Be familiar with pathological progression: endothelial dysfunction → lipid accumulation → foam cells → fibrous cap → rupture → thrombosis.

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