Observations Regarding Potential Mechanisms

more complications occurred in six patients (9%), including non-Q wave myocardial infarction (three patients, 4.5%), femoral arterial injury requiring surgical repair (two patients, 3%), and proximal dissection leading to emergency bypass surgery (one patient, 1.5%). Despite these favorable acute results, the 6-month lesion restenosis rate was 30% by life-table analysis. Light microscopy of retrieved tissue revealed atherosclerotic plaque in 94%, media in 67%, and adventitia in 27%. Intimal proliferation was present in 97% of the restenosis lesions but was also evident in 33% of primary lesions. Tissue weight from 27 lesions averaged 18.5 mg (range, 5.8-45.1 mg), which is not adequate to explain the entire angiographic improvement. Thus, part of the improvement in lumen diameter appears to be due to mechanical dilatation rather than to tissue removal alone. Atherectomy can predictably treat selected coronary lesions with overall safety comparable to that of conventional balloon angioplasty, although the procedure