Microemboli and Microvascular Obstruction in Acute Coronary Thrombosis and Sudden Coronary Death: Relation to Epicardial Plaque Histopathology

Objectives: This study examined myocardial microvascular emboli and obstruction, and related these to plaque in the epicardial coronary arteries supplying the affected microvessels.

Background: Epicardial coronary thrombosis often causes microemboli and microvascular obstruction. The consequences of myocardial microvessel obstruction and myocyte necrosis are substantial, yet histopathologic characterization of epicardial coronary artery plaque has been incompletely characterized. This study examined myocardial microvascular emboli, and related these to plaque in the coronary arteries supplying the microvessels.

Methods: Hearts from sudden coronary death patients underwent examination for coronary artery plaque type and cardiac microemboli.

Results: Forty-four hearts were available for evaluation. Mean age at death was 51 +/- 15 years. Coronary artery analysis found 26 plaque ruptures and 21 erosions, and a mean of 4.5 microemboli per heart. Microemboli and microvascular obstruction occurred most often from eroded plaques. Microemboli and occluded intramyocardial vessels were most common in the left anterior descending coronary artery, and all vessels contained fibrin and platelets. Mean stenoses of the culprit lesion was 74% in those with emboli and 75% in those without (p = NS). Intramyocardial microemboli were more common in plaque erosion than in rupture. Microvessels <200 mum were most often those that were occluded.

Conclusions: Microemboli and microvascular obstruction are common in patients dying of acute coronary thrombosis. Plaque erosion is more likely to cause emboli in vessels <200 mum. These emboli and microvessel obstruction have a prominent clinical role since myonecrosis is often associated with these findings.