Coronary angiography in a 48-year-old female smoker presenting with acute myocardial infarction shows only mild luminal irregularities despite complete occlusion of the mid-left anterior descending artery by thrombus. Autopsy material from a similar case shows thrombus overlying an intact endothelial surface with a plaque rich in smooth muscle cells and proteoglycans but no breach of the fibrous cap. Which mechanism caused the occlusion?

• A Plaque rupture through a thin fibrous cap exposing the necrotic core
• B Coronary artery embolism from a mural thrombus in the left atrium
• C Intraplaque hemorrhage from vasa vasorum rupture without luminal thrombus
• D Plaque erosion with thrombus formation on a denuded but structurally intact plaque surface ✓

Explanation

Plaque erosion accounts for roughly a quarter of fatal coronary thrombi and is disproportionately seen in younger women and smokers. Unlike plaque rupture, erosion shows thrombus superimposed on an intact endothelium over a plaque that is smooth muscle cell and proteoglycan rich, with a small lipid core and no cap disruption. Plaque rupture would expose the necrotic lipid core through a disrupted thin cap. Intraplaque hemorrhage causes plaque expansion but not acute total occlusion.

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

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Written and medically reviewed by the StethoPrep medical team.