Coronary morphology after percutaneous directional coronary atherectomy in humans: autopsy analysis of three patients. The morphologic basis of angiographically successful percutaneous directional atherectomy and subsequent restenosis in human coronary arteries is unknown. The clinical and pathologic features of three patients who died after coronary atherectomy are described. Tissue fragments obtained with atherectomy demonstrated atheromatous and fibroproliferative intima, media and adventitia. At autopsy, treated vascular segments (from the left anterior descending artery in two patients and a vein graft in one patient) demonstrated discrete defects in the vascular wall. Defects extending into atheroma, media or adventitia corresponded with the presence of these tissues in the atherectomy specimens. Tissues were otherwise not disrupted in the manner associated with balloon angioplasty. Acute mural thrombus deposition was evident in the resection zone in one patient. Late findings included fibroproliferative intimal tissue extending from the resected areas into the vascular lumen. In one patient intimal hyperplasia was sufficient to narrow the vascular lumen by 82% and was implicated in subsequent myocardial ischemia and infarction. The study indicates that 1) the vascular injury associated with atherectomy is distinct from that associated with balloon angioplasty, 2) acute mural thrombus deposition may occur even with resection limited to the intima, and 3) intimal hyperplasia may develop in regions treated with atherectomy and may be associated with late myocardial ischemia and infarction. 