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 < 0.0001), heart rate from 70 ± 10 to 66 ± 7 beats/min (p < 0.05) and the pressure-rate product from 10,322 ± 2,344 to 7,717 ± 1,650 (p < 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 < 0.005). Systemic and pulmonary resistances also decreased significantly (p < 0.0001 andp < 0.01, respectively). Coronary sinus flow increased from 107 ± 26 to 118 ± 25 ml/min (p < 0.01) and coronary vascular resistance decreased from 1.0 ± 0.2 to 0.77 ± 0.1 mm Hg/ml per min (p < 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.