UNDERESTIMATION OF EXTENT AND SEVERITY OF CORONARY-ARTERY DISEASE BY DIPYRIDAMOLE STRESS TL-201 SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHICMYOCARDIAL PERFUSION IMAGING IN PATIENTS TAKING ANTIANGINAL DRUGS

Objectives. This study evaluated the diagnostic value of dipyridamole plus low level treadmill exercise (dipyridamole stress) thallium-201 s ingle-photon emission computed tomography (SPECT) in patients taking a ntianginal drugs. Background. Dipyridamole stress is the major substit ute for maximal exercise in patients referred for myocardial perfusion imaging. Although antianginal drugs are commonly suspended before exe rcise, dipyridamole stress is usually performed without discontinuing these drugs. Methods. Twenty-six patients underwent two dipyridamole p erfusion studies: the first without (SPECT-1) and the second with (SPE CT-2) antianginal treatment, Twenty-one patients (81%) received calciu m antagonists, 19 (73%) received nitrates, and 8 (31%) received beta-b lockers. Eighteen of the patients underwent coronary angiography. Data are presented as the mean value +/- SD. Results. Visual scoring yield ed significantly larger and more severe reversible perfusion defects f or SPECT-I than for SPECT-2. Quantitative analysis showed larger perfu sion defects on stress images of SPECT-1 in the left anterior descendi ng coronary artery (LAD) (25 +/- 21% vs. 17 +/- 5%, p = 0.003), left c ircumflex coronary artery (LCx) (56 +/- 35% vs. 48 +/- 36%, p = 0.03) and right coronary artery (RCA) (36 +/- 27% vs. 25 +/- 24%, p = 0.008) territories. Individual vessel sensitivities in the LAD, LCx and WCA territories mere 93%, 79% and 100% for SPECT-1 and 64%, 50% and 70% fo r SPECT-2, respectively. These differences were highly significant for the LAD (p = 0.004) and LCx (p = 0.00004) territories. The overall in dividual vessel sensitivity of SPECT-1 was significantly higher than t hat of SPECT-2 (92% vs. 62%, p = 0.000003). Specificity was not signif icantly different in SPECT-1 compared with SPECT-2 (80% and 93%, p = 0 .33). Conclusions. Continued use of antianginal drags before dipyridam ole plus low level treadmill exercise thallium-201 SPECT may reduce th e extent and severity of myocardial perfusion defects, resulting in un derestimation of coronary artery disease. (C) 1998 by the American Col lege of Cardiology.