Effects of nifedipine on myocardial perfusion and ischemic injury in dogs.

To determine whether nifedipine, a calcium antagonist, protects ischemic myocardium, conscious dogs were subjected to coronary occlusion and given nifedipine by intravenous infusion beginning 30 minutes after the onset of ischemia and lasting for 24 hours while systemic arterial pressure, left atrial pressure, and cardiac output were monitored. Local myocardial perfusion at selected intervals after coronary occlusion was assessed with radioactive microspheres injected into the left atrium. In regions of myocardium exhibiting moderately depressed flow 29 minutes after occlusion in control dogs (n = 8), flow was significantly greater 3 and 23.5 hours later, reflecting increases in collateral perfusion. Corresponding zones of myocardium in treated dogs (n = 9) exhibited significantly greater increases in flow at each interval after occlusion (P less than 0.05). Furthermore, myocardial creatine kinase depletion (which correlated well with morphometric estimates of necrosis) in myocardium matched for ischemia prior to treatment was 1.5 to 3 times less in treated than in control dogs (P less than 0.05). Thus, nifedipine produced sustained increases in collateral flow and reduced myocardial ischemic injury.