[Comparative evaluation of the effect of nitroglycerin, sodium nitroprusside and phentolamine on hemodynamics and myocardial contraction during coronary occlusion in the dog].

Acute experiments on 27 dogs were conducted to examine the effect of intravenous nitroglycerin, sodium nitroprusside and phentolamine on the hemodynamics and regional contractility of the left ventricle under conditions of experimental coronary occlusion. Nitroglycerin was the most effective agent versus the other drugs in decreasing the elevated diastolic pressure in the left ventricle whereas sodium nitroprusside showed the most pronounced hypotensive effect in relation to systemic arterial pressure. All these drugs produced indirect favourable chrono- and inotropic effects especially marked with phentolamine. The effect of nitroglycerin and sodium nitroprusside on the cardiac output may vary to a great extent: a decrease in the stroke volume occurred in the presence of the remaining high degree of peripheral vascular resistance and a fall in the elevated and diastolic pressure in the left ventricle, an increase in the stroke volume was observed in the case of a considerable drop in the overall peripheral vascular resistance and the persisting endodiastolic overburden of the left ventricle.