The aim of this double-blind, placebo-controlled, cross-over study was to assess the cardioprotective effect of intracoronary nifedipine during percutaneous transluminal coronary angioplasty balloon occlusion. A balloon inflation without drug injection was initially made to ascertain that a shift of the ST segment (> or = 2 mm, 0.08 s after the J point) appeared (inclusion criterion). Two other balloon inflations were preceded by intracoronary injection of either 0.2 mg nifedipine or placebo, distal to the stenosis through the balloon catheter. The evaluation criteria were (1) time to ST segment shift, and (2) maximal amplitude of ST segment shift caused by balloon occlusion. Comparison of the data used an analysis of variance. Sixty-seven patients (mean age 54 +/- 8 years; 54 male, 13 female) were studied; 50 patients had 1-, 16 patients 2- and 1 patient 3-vessel disease. The dilated vessel was the left anterior descending coronary artery (n = 51), the right coronary artery (n = 12) and the left circumflex coronary artery (n = 4). Balloon inflation time was 100 +/- 31 s in the nifedipine group and 93 +/- 29 s in the placebo group. Five patients were excluded (procedure stopped after the first inflation in 1 and ST segment shift < 2 mm during the first inflation in 4). The time to 2-mm ST segment shift was longer in the nifedipine group than in the placebo group (62 +/- 40 s versus 51 +/- 40 s, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)