Influence of nifedipine on collateral blood flow during acute ischemia in the dog.

Vasodilators have been found effective in increasing blood flow in the lateral border surrounding a central zone of infarction, but any change in blood flow to this border zone may be to the normal tissue in this zone, rather than to the ischemic tissue. In this study of the effects of nifedipine on collateral blood flow, 31 open chest dogs underwent coronary occlusion followed by nifedipine infusion, either 3 or 1 microgram/kg per min. A balloon perfusion microsphere labeling device was used to separate the influence of normally perfused tissue overlapping with ischemic tissue in the lateral border zone. Nifedipine increased blood flow in the border zone, but this increase could be accounted for by the effect of nifedipine on admixed normal tissue. In the central ischemic zone, nifedipine administration resulted in a decrease in collateral blood flow. Thus, to fully understand the effect of a vasodilator on ischemic zone blood flow, it is necessary to account for flow in overlapping normal tissue.