Which combination of histological features defines the vulnerable (unstable) coronary plaque that is most likely to rupture and precipitate acute myocardial infarction?

• A Thick fibrous cap, small lipid core, abundant smooth muscle cells
• B Concentric stenosis occupying greater than 90% of the lumen
• C Extensive calcification with dense collagen and minimal inflammation
• D Thin fibrous cap under 65 micrometers, large lipid core exceeding 40% of plaque area, numerous macrophages, depleted smooth muscle cells ✓

Explanation

Rupture-prone plaques have a thin cap rich in matrix-degrading metalloproteinases released by activated macrophages, a large lipid pool loaded with tissue factor, and loss of smooth muscle cells that normally repair the cap. Inflammation thins the fibrous covering until it tears. Heavily calcified, densely collagenous, or severely stenotic plaques are typically stable; most infarct-causing ruptures occur in mildly to moderately stenotic plaques.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.