IMPACT OF ACUTE PROPRANOLOL ADMINISTRATION ON DOBUTAMINE-INDUCED MYOCARDIAL-ISCHEMIA AS EVALUATED BY MYOCARDIAL PERFUSION IMAGING AND ECHOCARDIOGRAPHY

Beta-blocker therapy may delay or completely prevent myocardial ischem ia during exercise testing, as assessed by ST-segment shifts, myocardi al perfusion defects, or echocardiographic wall motion abnormalities. However, the impact of beta-blocker therapy on these end points during dobutamine stress testing has not been well established. The purpose of this study was to determine the impact of propranolol on dobutamine stress testing with ST-segment monitoring, technetium-99m (Tc-99m) se stamibi single-photon emission computed tomography (SPECT) imaging, an d echocardiography. In 17 patients with known reversible perfusion def ects, dobutamine stress tests with and without propranolol were perfor med in randomized order and on separate days, following discontinuatio n of oral beta blockers and calcium antagonists. Propranolol was admin istered intravenously to a cumulative dose of 8 mg or to a maximum hea rt rate reduction of 25% and dobutamine was infused in graded doses in 3 minute stages until a standard clinical end point or the maximum do se of 40 mu g/ kg/min was achieved. The dobutamine stress test after p ropranolol was associated with a lower maximum heart rate (83 +/- 18 v s 125 +/- 17, p <0.001) and rate pressure product (14,169 +/- 4,248 vs 19,894 +/- 3,985, p <0.001) despite a higher infusion dose. The SPECT myocardial ischemia score was also lower (6.9 +/- 5.8 vs 10.1 +/- 7.1 , p = 0.047) and fewer echocardiographic segments were abnormal (3.4 /- 3.0 vs 4.6 +/- 3.4, p = 0.042). In 4 of 17 patients, reversible per fusion defects and echocardiographic wall motion abnormalities were de tected during the control but not during the propranolol test. Thus, d uring dobutamine stress testing, beta-blocker therapy attenuates, and in some cases eliminates, evidence of myocardial ischemia. (C) 1997 by Excerpta Medica, Inc.