Influence of nifedipine on coronary haemodynamics and myocardial metabolism in coronary artery disease.

The effect of 30 mg sublingual nifedipine on cardiac metabolism and haemodynamics was studied during two identical periods of pacing in 11 patients with chronic coronary artery disease. The pace time to angina pectoris improved after nifedipine in 6 patients, deteriorated in 2 and was unchanged in 3. Nifedipine decreased blood pressure (12%), rate pressure product (10%) and coronary vascular resistance (17%) during pacing. Aorto-coronary sinus (A-Cs) oxygen difference decreased at rest (9%) and postpacing (10%) after nifedipine, although an opposite tendency in coronary sinus blood flow resulted in unchanged myocardial oxygen uptake throughout the study. Although mean myocardial lactate extraction after nifedipine was unchanged during pacing in the whole group of patients, it increased in 9 patients who showed a net lactate release at control pacing (from -50.9 +/- 33.5% to -35.9 +/- 30.2%, P less than 0.05). Nifedipine increased free fatty acid (FFA) extraction during pacing (from 1.5 +/- 12.9% to 17.4 +/- 13.1%, P less than 0.02) and uptake (from 1.8 +/- 8.5 to 11.1 +/- 10.6 mu mol min-1, P less than 0.05). Nifedipine influenced only glucose exchange significantly (46% decreased extraction) at 5 min postpacing. The A-Cs citrate gradient lessened 30-40% postpacing after nifedipine administration. Since the unloading effects of nifedipine did not alter myocardial oxygen uptake, the most important net haemodynamic finding was the decrease in coronary vascular resistance. Although no significant antianginal effect of a fixed dose of nifedipine was found, the increased uptake of FFA may reflect improved myocardial oxidative metabolism after nifedipine.