Alterations in regional myocardial blood flow after nitroprusside and nitroglycerin in patients with and without significant coronary artery disease

Abstract

To evaluate vasodilator-induced redistribution of regional myocardial blood flow, intravenous sodium nitroprusside and nitroglycerin were administered in doses producing matched reductions (15%) in mean arterial pressure at constant heart rate. Anterior left ventricular great cardiac vein blood flow (thermodilution) was measured in 14 patients without angiographic anterior collateral supply. Global coronary sinus blood flow remained constant with both nitroprusside and nitroglycerin administration, despite significant reductions in mean arterial pressure. However, nitroglycerin reduced great vein flow by 25 ± 17% and nitroprusside by 10 ± 16% (p < 0.01). Subgroup analysis indicated that the nitroglycerin-nitroprusside regional blood flow differences were more pronounced in patients without significant left anterior descending coronary artery narrowing. Neither vasodilator produced significant differences in arterial-coronary sinus oxygen or lactate contents, calculated myocardial oxygen consumption, left ventricular dP/dt, or electrocardiographic or clinical signs of myocardial ischemia. Despite qualitatively similar hemodynamic effects, comparisons of vasodilator-induced relative reductions in normally supplied anterior left ventricular regional coronary blood flow suggest a mechanism of the reported beneficial effects of nitoglycerin on potentially ischemic myocardial regions.