Effects of felodipine, a new dihydropyridine vasodilator, on regional myocardial blood flow during acute coronary occlusion in the pig

We studied the effects of felodipine [4-(2,3-dichlorophenyl)-1,4-dihydropyridine-2,6-dimethyl 3,5-dicarboxylic 3-ethylester and 5-methylester] on the coronary vascular bed of pig hearts with an ischemic region in the left ventricle following ligation of the left anterior descending coronary artery. At an infusion rate of 0.12 nmol X kg-1 X min-1, felodipine caused a slight reduction in mean arterial blood pressure and a decrease in coronary vascular resistance in both normal myocardium and partly ischemic myocardium of the border zone. In another series of experiments, felodipine was infused at a higher rate (0.38 nmol X kg-1 X min-1). The resultant decrease in mean arterial blood pressure, which was about 30%, was counterbalanced by inflation of an aortic balloon to keep the afterload and the coronary perfusion pressure constant. In this situation, felodipine caused a pronounced increase in blood flow to all parts of the heart except the central ischemic zone, where blood flow was extremely low. We conclude that felodipine has a coronary vasodilator action which is at least of the same magnitude as its peripheral vasodilator action, and that it markedly increases coronary blood flow in the border zone of an ischemic area.