Effect of propranolol on postexercise left ventricular ejection time index.

The net delta left ventricular ejection time index 4 minutes after exercise is prolonged in many patients with coronary artery disease. This prolongation is thought to be due to the lack of response of the ischemic myocardium to adrenergic stimulation and has been proposed as a measure of myocardial ischemia. In this study, the effect of beta adrenergic blockade on net delta left ventricular ejection time was studied in nine normal subjects (Group A) and in eight patients with stable angina and coronary artery disease (Group B). In Group A, a treadmill exercise test was performed for 10 minutes before and after administration of propranolol, 160 mg daily, for 2 days. The postexercise net delta left ventricular ejection time was significantly greater after propranolol (mean +/- standard error of the mean 12 +/- 4 versus 35 +/- 4 ms, p less than 0.01). In group B a maximal treadmill exercise test was performed before and after therapy with propranolol. Only patients with a normal net delta left ventricular ejection time before propranolol were selected. The net delta left ventricular ejection time again increased significantly after propranolol (11.5 +/- 4 versus 35.3 +/- 5 ms p less than 0.01). It is concluded that prolongation of postexercise net delta left ventricular ejection time cannot be used to diagnose ischemia in patients who are receiving propranolol therapy. Our data support the hypothesis that prolongation of net delta left ventricular ejection time after exercise is caused by an impaired myocardial response to catecholamines, whether due to ischemia or effective beta adrenergic blockade.