A 52-year-old obese man with hypertension and hypercholesterolemia dies suddenly. Autopsy reveals a ruptured atherosclerotic plaque in the proximal left anterior descending coronary artery with overlying occlusive thrombus. The plaque has a large lipid core occupying >40% of plaque volume, a thin fibrous cap infiltrated by macrophages, and minimal calcification. Which of the following features MOST contributed to plaque vulnerability and rupture?

• A Heavy calcification of the plaque core making it brittle
• B Macrophage-derived MMP secretion thinning the fibrous cap ✓
• C Smooth muscle cell proliferation increasing plaque bulk
• D Endothelial hyperplasia forming a thick protective cap

Explanation

Vulnerable (unstable) plaques are characterized by a large necrotic lipid core, thin fibrous cap, and abundant macrophage infiltration. Macrophages (foam cells) secrete matrix metalloproteinases (MMPs) that degrade the collagen and extracellular matrix of the fibrous cap, making it susceptible to rupture under shear stress. Smooth muscle cells actually stabilize plaques by synthesizing fibrous cap collagen; heavy calcification is more a feature of stable plaques.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.