Effects of intravenously administered propranolol on wall motion abnormalities

Abstract

Although propranolol is frequently utilized as therapy for angina pectoris in patients with previous myocardial infarction, its effects on wall motion abnormalities in such patients have not been adequately defined. Accordingly, using external wall motion video tracking, we studied 18 patients with previous myocardial infarction and wall motion disorders and 5 normal subjects before and after administration of propranolol, 5 mg intravenously. Systolic time intervals, heart rate and left heart size (measured by the distance between the mid-line and left heart border in an X-ray film triggered at end-diastole after a standard inspiration) were also measured before and after administration of propranolol. In each instance propranolol produced a reduction in the amplitude and velocity of wall motion in areas of normal movement, hypokinesis and paradox, resulting in decreased outward bulging. In the normal subjects, the amplitude and velocity of wall motion also decreased. In the patients with previous myocardial infarction, propranolol increased the ratio of the preejection period to the left ventricular ejection time from a mean of 0.377 ± 0.03 (standard error of the mean) to 0.409 ± 0.03 ( P <0.001); decreased heart rate by an average of 7.5 beats/min ( P <0.001); and increased the distance from the mid-line to the left heart border from 94.3 ± 2.6 to 97.3 ± 2.6 mm ( P <0.001). Similar changes occurred in the 5 normal subjects. We conclude that doses of propranolol sufficient to increase the ratio of the preejection period to left ventricular ejection time, decrease heart rate and increase heart size do not exaggerate preexisting paradoxical wall motion or accentuate latent areas of paradox in patients with previous myocardial infarction.