QUALITATIVE AND QUANTITATIVE CONTRASTS IN THE MECHANISMS OF LUMEN ENLARGEMENT BY CORONARY BALLOON ANGIOPLASTY AND DIRECTIONAL CORONARY ATHERECTOMY

Objectives. This study was designed to define and contrast the mechani sms of lumen enlargement from coronary balloon angioplasty and directi onal coronary atherectomy using intracoronary ultrasound imaging in vi vo. Background. The mechanisms of lumen enlargement produced by percut aneous transluminal coronary balloon angioplasty and directional coron ary atherectomy are not known because the coronary artery wall has not previously been studied both before and after dilation. Methods. We u sed intracoronary ultrasound to quantitate coronary lumen, vessel and plaque area both before and immediately after successful coronary angi oplasty (n = 30) and directional coronary atherectomy (n = 25) at the site of most severe stenosis. Results. Angioplasty increased lumen are a by 2.80 +/- 0.25 mm2 (mean +/- SE, p < 0.0001). Eighty-one percent o f this lumen gain resulted from an increase in vessel area and the rem aining 19% from a reduction in plaque area. Lumen gain of individual l esions was separated into three groups: 67% had an increase in vessel area (vessel expansion), 13% had a decrease in plaque area and 20% had a combination of both. In contrast, vessel expansion contributed only 22% of the lumen gain with directional coronary atherectomy, with the majority (78%) of increase in lumen size coming from a reduction in p laque area. Directional coronary atherectomy increased lumen area from 2.36 +/- 0.05 to 7.00 +/-0.28 mm2 (p < 0.0001). Plaque reduction was the sole mechanism in 60% of lesions, vessel expansion was the sole me chanism in 12% and a combination of both mechanisms occurred in 28%. L umen enlargement of eccentric lesions treated with directional coronar y atherectomy was more commonly associated with plaque reduction (p < 0.02), whereas eccentricity did not affect the mechanism of lumen enla rgement with coronary angioplasty. Conclusions. This is the first stud y to systematically examine the coronary artery wall in vivo at the si te of a severe stenosis both before and after catheter-based intervent ions in humans. Lumen enlargement from coronary angioplasty occurs pre dominantly from vessel expansion or stretching, although a reduction i n plaque area contributes to the lumen gain in many patients and is th e sole mechanism in a few. Lumen gain from directional coronary athere ctomy is predominantly from reduction in plaque area (probably owing t o tissue removal), although vessel stretching (balloon effect) occurs and is the sole mechanism in a small minority of vessels. Plaque reduc tion is more common in directional coronary atherectomy of eccentric l esions.