MECHANISMS OF ANGIOGRAPHICALLY SUCCESSFUL DIRECTIONAL CORONARY ATHERECTOMY - EVALUATION BY INTRACORONARY ULTRASOUND AND COMPARISON WITH TRANSLUMINAL CORONARY ANGIOPLASTY

To assess the mechanisms of luminal improvement, 40 patients undergoin g directional coronary atherectomy and a matched control group of 25 p atients undergoing angioplasty were evaluated with intracoronary ultra sound imaging before and after intervention. Despite similar sized ves sels, a similar angiographic severity of diameter stenosis (75 +/- 12% for the angioplasty group vs 69 +/- 15% for the atherectomy group, p = NS), and a similar plaque burden (percent plaque area) before interv ention (84 +/- 5% in the angioplasty group vs 85 +/- 13% in the athere ctomy group, p = NS), the residual plaque area after intervention was significantly smaller in the atherectomy group (54 +/- 14%) compared w ith the angioplasty group (65 +/- 13%, p = 0.002). Despite excellent a ngiographic results, significant residual plaque was noted after eithe r successful intervention. Based on the absolute changes in lumen area , plaque area, and vessel area, improvement in the lumen area in the a therectomy group occurred as a result of plaque ''compression'' (48%), plaque removal (37%), and vessel expansion (15%). In the angioplasty group, plaque ''compression'' accounted for 94% of the improvement in lumen area, whereas vessel expansion contributed 6%. Thus ''compressio n'' of plaque remains the major mechanism of luminal improvement durin g atherectomy.