Frequency and characteristics of coronary thrombosis in the epicardial coronary arteries after cardiac transplantation.

We investigated at autopsy or at retransplantation the frequency and characteristics of coronary thrombosis in 76 cardiac allografts: 37 in place for < or = 2 months (early) and 39 in place >2 to 99 months (late). The 76 allografts were inserted in 69 patients: a single 1 in 56 patients and 2 allografts in 13 patients, 7 of whom subsequently died and had an autopsy. An average of 140 sections from 70 5-mm-long segments of 8 epicardial coronary arteries were examined from each of the 76 allografts with both hematoxylin-eosin and Movat pentachrome stains. Thrombus was found in only 1 coronary artery (3%) (the right one) of the 37 early allografts, and in 24 of 39 late allografts (61%). Of the latter 39 grafts, 29 (79%) had allograft vascular disease (AVD) and 24 (83%) of them had coronary thrombosis. Of the 312 epicardial coronary arteries (4 major and 4 minor) examined in the 39 late cases, 66 arteries (21%) contained thrombus. Of the 24 late cases with thrombus in at least 1 artery, thrombus was present in 66 (34%) of the 192 epicardial coronary arteries examined: in 6 of the 8 arteries in 3 patients; in 5 arteries in 2 patients; in 4 arteries in 1 patient; in 3 arteries in 5 patients; in 2 arteries in 6 patients, and in a single artery in 7 patients. In all 66 arteries with thrombus (24 patients) the thrombus was longer than 5 mm. The thrombus in the late cases was entirely nonocclusive (mural) in 51 (77%) of the 66 epicardial coronary arteries containing thrombus and entirely occlusive in 10 arteries (15%). It consisted exclusively of multiluminal channels in 6 arteries (9%) and combinations in 1 artery (2%). Acute myocardial infarcts were present in 3 patients, all of whom had occlusive thrombi. In all 10 arteries with occlusive thrombi, the thrombus was larger than the underlying plaque and no occlusive thrombi were located over ulcerated plaques. These observations demonstrate that thrombus is common in epicardial coronary arteries >2 months after cardiac transplantation.