Nitroglycerin-induced reduction in the incidence of spontaneous ventricular fibrillation during coronary occlusion in dogs

Previous investigations have demonstrated that nitroglycerin reduces ischemic injury and enhances ventricular electrical stability during coronary occlusion in dogs. These beneficial effects were potentiated by preventing drug-induced hypotension with alpha adrenergic agonists. To determine whether nltroglycerin can prevent spontaneous post-occlusion ventricular fibrillation, 27 open chest dogs were assigned in random fashion to two groups-control (saline infusion) and nitroglycerin-treated (0.45 mg intravenous bolus infusion followed by 0.3 mg/ min continuous infusion). After 10 minutes of infusion the left anterior descending and septal coronary arteries were occluded at their origins. Hypotensive effects of nitroglycerin were prevented by intermittent intravenous doses of methoxamine; mean arterial pressure and heart rate in control and treated animals were thus indistinguishable. Infusions continued until ventricular fibrillation occurred or 30 minutes elapsed. Twelve of 13 control dogs died with ventricular fibrillation; only 7 of 14 nitroglycerin-treated dogs died (P < 0.05). Thus, nitroglycerin may be capable of exerting important and unique beneficial effects in patients with acute myocardial infarction since, with its hypotensive effects obviated by alpha adrenergic agonists, it markedly diminishes ischemic injury, enhances ventricular electrical stability, and significantly reduces the incidence of spontaneous ventricular fibrillation in an experimental model of acute myocardial infarction.