Ventricular function and coronary hemodynamics after intravenous nitroglycerin in coronary artery disease

Abstract

Left ventricular dynamics as well as systemic and coronary hemodynamics were determined in 14 patients with coronary artery disease (1) under control conditions, (2) under intravenous infusion of nitroglycerin, (3) under continued infusion of nitroglycerin with restored arterial and pulmonary artery pressures induced by the parallel infusion of dextran. Heart rate was kept constant by atrial pacing. Intravenous nitroglycerin infusion resulted in a significant reduction in left ventricular systolic (20 per cent) and end-diastolic pressure (43 per cent), peak dp dt (13 per cent), cardiac index (16 per cent), stroke volume index (15 per cent), and stroke work index (30 per cent). Peak (dp/dt/total pressure) increased (15 per cent). Pulmonary vascular resistance markedly decreased (29 per cent), whereas total peripheral resistance did not change significantly (−3 per cent). Both coronary blood flow of the left ventricle (13 per cent) and myocardial oxygen consumption (15 per cent) decreased parallel to the reduction in preload and afterload. The action of nitroglycerin at restored left ventricular and pulmonary artery pressures was characterized by increase in peak dp dt (12 per cent), peak ( dp dt total pressure) (18 per cent), cardiac index (13 per cent), stroke volume index (14 per cent), and stroke work index (10 per cent). Both coronary blood flow (28 per cent) and myocardial oxygen consumption (21 per cent) increased parallel to the enhancement of ventricular performance. The results demonstrate that intravenous nitroglycerin produces effective diastolic and systolic unloading of the heart associated with reduction in myocardial oxygen consumption and in coronary blood flow. There was marked vascular pooling which quantitatively averaged 437 ± 128 ml. This occurred concomitant with a 43 per cent decrease in left ventricular end-diastolic pressure or a 20 per cent decrease in peak systolic pressure. Significant coronary dilating properties of nitroglycerin could not be detected in these coronary patients. The increase in left ventricular contractility indices at restored pressure suggests a moderate but significant positive inotropic effect of nitroglycerin.