Hemodynamic and coronary effects of intravenous labetalol in coronary artery disease.

Labetalol, an alpha and beta receptor blocking agent, was evaluated in 11 patients with documented coronary artery disease and stable angina. The mean dose of labetalol was 1.5 (range 1 to 2) mg/kg. Cardiovascular effects began within 1 minute after injection and were maximal within 10 minutes. Mean arterial pressure decreased from 105 +/- 13 to 81 +/- 10 mm Hg (p less than 0.0001), heart rate from 70 +/- 10 to 66 +/- 7 beats/min (p less than 0.05) and the pressure-rate product from 10,322 +/- 2,344 to 7,171 +/- 1,650 (p less than 0.001). Cardiac output and pulmonary wedge pressure did not change significantly. Mean pulmonary arterial pressure decreased from 20 +/- 3 to 16 +/- 2 mm Hg (p less than 0.005). Systemic and pulmonary resistances also decreased significantly (p less than 0.0001 and p less than 0.01, respectively). Coronary sinus flow increased from 107 +/- 26 to 118 +/- 25 ml/min (p less than 0.01) and coronary vascular resistance decreased from 1.0 +/- 0.2 to 0.77 +/- 0.1 mm Hg/ml per min (p less than 0.001). Labetalol may be a useful adjunct in the treatment of angina not only because it diminishes myocardial oxygen requirements but also because it improves coronary hemodynamics. Thus, labetalol appears to have some advantage compared with the usual beta blocking agents with their potentially detrimental effects on coronary hemodynamics.