Systemic and coronary hemodynamics of labetalol in normotensive patients with ischemic heart disease

Summary

The systemic and coronary hemodynamic effects of combined alpha- and beta-adrenergic blockade produced by labetalol were assessed in 24 normotensive patients with angina pectoris and an ischemic electrocardiographic response to exercise stress. Both the intravenous (0.5 mg/kg) and oral (200 mg) formulations of labetalol were evaluated. At rest, labetalol produced systemic vasodilation (systemic vascular resistance-16% after intravenous and-8% after oral labetalol, both p<0.05) without change in heart rate. Aortic pressure usually was lower and cardiac output preserved or increased. Left ventricular end-diastolic pressure was unchanged. Coronary sinus flow was usually unchanged after either route of administration. Exercise duration was prolonged in 14 of the 20 patients with severe coronary artery disease. During exercise, tachycardia was blunted (-12% after intravenous,-7% after oral labetalol, both p<0.05) as was the increase in mean aortic pressure (-12% and-13% intravenous and oral labetalol respectively, both p<0.05), left ventricular end-diastolic pressure [-7% and-1%, respectively, both p=not significant (NS)] was unchanged. Coronary sinus flow (-16% and-25%, respectively, both p<0.05) was decreased as heart rate and aortic pressure were lower. Cardiac output, systemic vascular resistance, and coronary vascular resistance were similar to control exercise. The hemodynamic effects of intravenous and oral labetalol are, in general, similar. Hemodynamic responses differ from those produced by other beta-blockers and by calcium antagonists.