The systemic and coronary haemodynamic effects of intravenous nicardipine were investigated in 10 patients with a more than 70 p. 100 stenosis of the left coronary artery. Two brief atrial pacing tests (ST1 and ST2) were performed. ST2 was performed 30 minutes after an intravenous injection of nicardipine 2.5 mg over 5 minutes. Nicardipine produced a 25 p. 100 decrease in ventricular systolic pressure and a substantial increase in cardiac index (from 2.74 +/- 0.48 to 3.46 +/- 0.35 l/min/m2, p less than 0.001). Measurement of the coronary flow rate by the thermodilution method showed a 40 p. 100 increase in sinus blood flow while coronary resistance decreased not only in territories with normal supply but also in myocardial territories distal to the coronary stenosis (from 2.76 +/- 2.3 to 1.83 +/- 1.5 mmHg/ml, p less than 0.02). With the same paced heart rate the ventricular function parameters were significantly improved during ST2 (cardiac index ST2 3.56 +/- 0.65 vs ST1 2.8 +/- 0.48, p less than 0.001; dp/dt max ST2 2143 +/- 369 vs ST1 1874 +/- 301 mmHg/sec, p less than 0.05), reflecting a lower degree of myocardial ischaemia. This was confirmed by the lower amplitude of electrocardiographic depression and by a higher lactate extraction coefficient (LE ST1 6 +/- 7 p. 100 vs LE ST2 12 +/- 12 p. 100, p less than 0.05). Mean arterial blood pressure and coronary sinus blood flow rate values were identical during the two atrial pacing tests.(ABSTRACT TRUNCATED AT 250 WORDS)