Comparison of the effects of nifedipine and nitroglycerin on coronary blood flow using intracoronary Doppler catheter.

Different effects of nifedipine and nitroglycerin on large coronary arteries measured by the Xenon washout method are well documented in early reports, but results of direct measurements of the flow velocity of the large vessels were inconsistent. The goal of this investigation was to compare the effects of nifedipine and nitroglycerin on coronary blood flow using an intracoronary Doppler catheter. Fourteen patients with normal coronary arteries (group 1) and eight (group 2) with coronary artery diseases (more than 75% concentric stenosis over the left anterior descending artery in the middle portion) were presented on diagnostic procedure for evaluation of chest pain or abnormal exercise tests after written informed consents. We compared the effects of nitroglycerin (0.6 mg) and nifedipine (10 mg) given sublingually on coronary blood flow velocity using a Doppler coronary catheter. The results indicated that the maximal increase in large coronary arterial diameter induced by nifedipine was similar to that induced by nitroglycerin. Nifedipine increased diastolic and systolic velocity area indices (DVAI and SVAI), and reduced diastolic and systolic coronary vascular resistance (DCVRI and SCVRI). In contrast, nitroglycerin reduced DVAI and SVAI and minimally increased DCVRI and decreased SCVRI in group 2 patients. The increased heart rate and decreased blood pressure induced by both drugs were similar. The differences in the rate-pressure product between the two drugs were not significant. Nifedipine increased flow velocity and decreased coronary vascular resistance, but nitroglycerin achieved the opposite effect, especially in patients with coronary artery disease.