Effect of Isoproterenol on Coronary Blood Flow in Primary Myocardial Disease

At cardiac catheterization, the effect of isoproterenol on coronary blood flow was compared in six patients with primary myocardial disease and six patients who appeared to have no cardiac disease. Coronary blood flow was measured by selective coronary artery injection of xenon-133 and external monitoring of disappearance curves with a dual probe, digital scintillation counter. In the presence of similar changes in cardiac output and heart rate-systolic pressure product, changes in coronary blood flow and coronary resistance in response to isoproterenol were significantly less ( P < 0.05) in the subjects with primary myocardial disease than in the normal subjects.