Effect of labetalol on indices of myocardial necrosis in patients with suspected acute infarction

Abstract

The role of combined alpha and beta blockade as a means of limiting infarct size has been studied in a randomised controlled trial using labetalol. Only 166 of 630 (26%) consecutive patients admitted to a cardiac care unit with suspected myocardial infarction were deemed suitable for inclusion; most of the remainder had delayed admission to hospital, were over the age limit of 75, or had complications which precluded the use of labetalol. Those on active treatment received a loading dose followed by a slow intravenous infusion over six hours, and oral therapy for the subsequent five days. Doses were adjusted to maintain systolic pressure in the range 100 to 120 mmHg. The control group received only conventional therapy. Labetalol caused lowering of the blood pressure and heart rate during the phase of intravenous treatment, but little effect occurred subsequently because oral dosage was constrained by low systolic pressures. The group that received active treatment had significantly greater release of CKMB enzyme. Little difference was observed in R wave scores or ejection fraction. Only low doses of labetalol can be used for most patients with acute myocardial infarction. Labetalol cannot be recommended as routine treatment for normotensive patients admitted to hospital with suspected infarction.