THERAPY AND PREVENTION

Esmolol is a new ultra short-acting (half-life [tl/2½] 9 min) /3I-adrenergic-receptor antagonist reported to have no intrinsic sympathomimetic activity. The safety and efficacy of esmolol in lowering the ventricular rate and rate-pressure product in patients with acute myocardial infarction (n = 5), postmyocardial infarction angina (n = 10), or acute unstable angina (n = 4), and without cardiogenic shock were studied. After a 30 min observation period, esmolol was titrated to a maximum dose of 300 gg/kg/min and infused for up to 420 min. The ventricular rate fell from 92 ± 11 (mean SD) to 77 + 13 beats/min (p < .01) and the systolic arterial pressure decreased from 120 ± 13 to 97 11 mm Hg (p < .01) during the initial 30 min titration period. There was no significant change during the maintenance phase, and both the ventricular rate and arterial pressure returned rapidly toward baseline values within 30 min of termination of the infusion. The cardiac index fell from 2.8 + 0.6 to 2.2 ± 0.6 liters/min/m2 (p < .01) during the same period, and also returned to the baseline level 30 min after termination of the infusion. There was no significant change in the pulmonary capillary wedge pressure, respiratory rate, or PR interval. Five patients required termination of infusion because of hypotension and all recovered uneventfully within 30 min of stopping the esmolol. One patient required a brief infusion of dopamine to restore hemodynamic stability. This experience suggests that in the absence of _fongestive heart failure or shock, esmolol is effective in slowing the heart rate and lowering the arterial pressure and the rate-pressure product in patients with acute myocardial ischemia. Furthermore, the hemodynamic effects are rapidly reversed after termination of infusion. Thus, esmolol may be of value in patients with acute myocardial ischemia in whom rapid titration of /-adrenergic blockade is clinically desirable.