EFFECT OF BETA-ADRENOCEPTOR BLOCKADE ON DIPYRIDAMOLE-INDUCED MYOCARDIAL ASYNERGIES IN CORONARY-ARTERY DISEASE

Twenty-one patients with angiographic evidence of significant coronary artery disease, and positive dypiridamole echocardiographic test results at basal condition and after 7 days of placebo treatment were prospectively studied to see whether beta-blockade modifies the effects of dipyridamole echocardiographic testing on regional myocardial contractility. Patients were randomized to propranolol (120 mg/day) or placebo treatment in 3 divided doses for 7 days, after which each patient crossed over to the alternate regimen. Dipyridamole-ecocardiographic testing was repeated at the end of each treatment. Propranolol abolished new mechanical signs of transient dipyridamole-induced ischemia (new wall motion abnormalities or an increase in degree of basal asynergies, or both) in 13 of 21 patients. The remaining 8 patients had positive results on dipyridamole echocardiographic testing after the propranolol treatment period. At basal conditions both heart rate and rate-pressure product were significantly reduced with propanolol; there was also a significant decrease in these parameters at peak dipyridamole infusion. At peak dipyridamole infusion heart rate and rate-pressure product were significantly lower in patients with negative than in those with positive echocardiographic test results after propanolol. Our data show that administration of beta-blockade significantly reduces the development of transient dipyridamole-induced myocardial asynergies, the earliest markers of acute myocardial ischemia, detected with 2-dimensional echocardiography.