DO BETA-BLOCKERS AFFECT THE DIAGNOSTIC SENSITIVITY OF DOBUTAMINE STRESS TL-201 SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHIC IMAGING

Background. The effects of beta-blockers on dobutamine stress Tl-201 t omographic imaging are not known, This study was undertaken to examine whether beta-blockers affect the sensitivity of dobutamine stress Tl- 201 imaging. Methods and Results. One hundred ten patients without pre vious myocardial infarction underwent dobutamine stress Tl-201 single photon emission computed tomography (SPECT) and coronary arteriography , both studies within a 1-week period, Dobutamine was infused at rates of 5, 10, 20, 30, and 40 mu g/kg/min in 3-minute stages, Atropine (as much as 1 mg) was injected intravenously when the patient's heart rat e was <100 beats/min, Patients in group 1 (n = 72) were receiving beta -blockers and patients in group 2 (n = 38) were not, The SPECT images in group 1 showed perfusion abnormalities in 62%, 87%, and 94% of pati ents with one-, two-, and three-vessel coronary artery disease (greate r than or equal to 50% diameter stenosis), respectively, compared with 75%, 71% and 100% in group 2 (p not significant), The overall sensiti vities mere 82% (37 of 45) in group 1 and 80% (16 of 20) in group 2 (p not significant), The specificities were 81% (22 of 27) in group 1 an d 83% (15 of 18) in group 2 (p not significant), The overall accuracie s were the same for both groups (82%), Atropine was added more often i n group 1 than in group 2 (37/72 vs 5/38, p < 0.001). Conclusions. Our results suggest that beta-blockers do not affect the sensitivity, spe cificity, and accuracy of dobutamine stress Tl-201 SPECT imaging for d etecting coronary artery disease if atropine is given when the chronot ropic response is inadequate, In patients receiving beta-blockers, how ever, the addition of atropine to dobutamine stress is more frequently required.