The acute and long-term results of percutaneous transluminal coronary angioplasty (PTCA) of the left coronary artery in 106 patients (group 1) with chronic occlusion of the right coronary artery were compared with those of 106 patients matched for sex (92 male) and age (56 +/- 10 years) undergoing left PTCA with a normal right coronary artery (group 2). Before the procedure, group 1 had more unstable angina (42 vs 29%; p < 0.05), more frequent prior myocardial infarction (80 vs 25%; p < 0.001), and a lower left ventricular ejection fraction (56 +/- 10% vs 65 +/- 11%; p < 0.005). Acute results were not different in the 2 groups with respect to primary success (group 1: 93%; and group 2: 89%) and complications (group 1: 2 with emergency coronary surgery, and 4 with periprocedural myocardial infarction and no death; and group 2: 1 with emergency coronary surgery, 1 death, and 3 with periprocedural myocardial infarction). At 6 months, 79 patients in group 1 and 71 patients in group 2 had reangiography; the rate of restenosis was 35% in group 1 and 42% in group 2. In both groups, left ventricular ejection fraction increased significantly in patients without restenosis (58 +/- 12% vs 63 +/- 10%, p < 0.001 [n = 44] in group 1; and 66 +/- 9% vs 70 +/- 10%, p < 0.001 [n = 29] in group 2). In group 1, improvement was significant only for patients without collaterals to the occluded right coronary artery (59 +/- 10% vs 66 +/- 7%; p < 0.003 [n = 24]).(ABSTRACT TRUNCATED AT 250 WORDS)