Effects of percutaneous transluminal coronary angioplasty on atherosclerotic plaques and relation of plaque composition and arterial size to outcome.

To delineate their relation to outcome of percutaneous transluminal coronary angioplasty (PTCA), the atherosclerotic plaque composition and coronary artery size in 82 five-mm long segments at 28 PTCA sites were determined in 26 patients having PTCA. The 26 patients were subdivided into 3 groups according to the degree of angiographic patency at the end of the PTCA procedure and to the duration of survival after PTCA (less than or equal to 30 or greater than 30 days): early success (13 patients, 16 PTCA sites and 49 five-mm segments); early failure (4 patients, 4 PTCA sites and 16 five-mm segments) and late success (9 patients, 8 PTCA sites and 17 five-mm segments). The mean percent of plaque comprised of fibrous tissue among the 3 groups was 80 +/- 18%, 71 +/- 23% and 82 +/- 16% (difference not significant); the mean percent of plaque comprised of lipid was 17 +/- 16%, 21 +/- 24% and 16 +/- 15% (difference not significant); and of calcium it was 3 +/- 4%, 8 +/- 10% and 2 +/- 3% (p = 0.01). The mean coronary arterial internal diameter was 3.3 +/- 0.6, 3.9 +/- 1.2 and 3.2 +/- 0.7 mm (p less than 0.02). Plaque tear was present in 1 or more histologic sections in 25 of the 26 patients and the 1 patient without it had the longest interval (nearly 3 years) between PTCA and death. Plaque tear extending from intima into media with dissection was observed only in the early and late success groups (p = 0.03). Hemorrhage into plaque was present in 16 (80%) of 20 PTCA sites in the 2 early groups and in 3 (37%) of 8 sites in the late group (p less than 0.03). Occlusive thrombus (5 of 16, 1 of 4 and 1 of 8) and plaque debris (7 of 16, 1 of 4 and 2 of 8) in residual lumens were insignificantly different among the 3 groups and their 82 five-mm segments. Plaques that had greater than 25% lipid content, however, had an increased frequency of hemorrhage into plaque (p less than 0.004), occlusive thrombus (p = 0.0001) and plaque debris in residual lumens (p less than 0.05). These findings suggest that coronary arterial size and plaque composition are strong determinants of PTCA outcome. The ideal coronary arterial atherosclerotic narrowing for both technically and clinically successful PTCA appears to be a small (less than 3.3 mm in internal diameter) artery in which the plaque contains relatively little calcium and lipid.