The hemodynamic effects of nisoldipine and diltiazem were investigated in two groups of patients undergoing investigation for suspected coronary artery disease. Emphasis was placed on the coronary hemodynamic changes. Approximately equihypotensive doses of these two calcium channel blockers, nisoldipine (6 micrograms/kg) and diltiazem (500 micrograms/kg) were given intravenously. Although both drugs decreased peak systolic pressure by 28% and 24%, respectively, heart rate increased with nisoldipine (68 +/- 9 to 82 +/- 12 bpm) and remained unchanged with diltiazem (70 +/- 9 to 67 +/- 10 bpm). Nisoldipine increased mean coronary sinus blood flow from 146 +/- 40 to 176 +/- 35 ml/min and great cardiac vein flow from 87 +/- 20 to 109 +/- 24 ml/min, producing a significant reduction in the calculated global (from 0.79 +/- 0.2 to 0.43 +/- 0.12 mmHg min/ml) and regional (from 1.43 +/- 0.2 to 0.70 +/- 0.13 mmHg min/ml) coronary vascular resistances. There were no significant flow changes when corrected for heart rate. Global and regional myocardial oxygen consumptions were not significantly altered. Diltiazem had no significant effects on heart rate or global and regional blood flows, although the vascular resistances decreased by 32% and 35%, respectively. Diltiazem reduced global and regional arterio-coronary sinus oxygen differences, resulting in significant decreases in global (from 14.9 +/- 4.7 to 12.1 +/- 2.3 ml/min) and regional (from 5.6 +/- 0.9 to 5.2 +/- 1.2 ml/min) myocardial oxygen consumptions. The major difference between the drugs was in heart rate, despite the similar reductions in aortic pressure. The lack of a positive chronotropic response after diltiazem may explain the reduction in myocardial oxygen consumption.