ARBUTAMINE STRESS TL-201 SINGLE-PHOTON EMISSION COMPUTED-TOMOGRAPHY USING A COMPUTERIZED CLOSED-LOOP DELIVERY SYSTEM - MULTICENTER TRIAL FOR EVALUATION OF SAFETY AND DIAGNOSTIC-ACCURACY

Objectives. This study sought to evaluate the efficacy and safety of a rbutamine when used in conjunction with thallium-201 single-photon emi ssion computed tomography (SPECT) in a multicenter trial and to compar e arbutamine stress and treadmill exercise thallium-201 SPECT for diag nostic sensitivity and myocardial perfusion pattern. Background. Arbut amine is a potent beta-agonist developed specifically for pharmacologi c stress testing. Methods. Arbutamine was administered by a novel comp uterized closed loop device that measures heart rate and adjusts arbut amine infusion to achieve a selected rate of heart rate increase towar d a predetermined limit. The cohort included 184 patients who underwen t arbutamine stress testing, of whom 122 (catheterization group) had a ngiographically defined coronary artery disease (greater than or equal to 50% diameter stenosis of a major coronary artery), and 62 had a lo w pretest likelihood of coronary artery disease (low likelihood group) . A subset of 69 patients from the catheterization group underwent bot h arbutamine and exercise stress testing. Results. Hemodynamic respons es during arbutamine and exercise stress testing demonstrated no signi ficant difference in percent increase in heart rate (81% vs. 76%) or s ystolic blood pressure (26% vs. 30%). The sensitivity for detecting co ronary artery disease (greater than or equal to 50% stenosis) using ar butamine thallium-201 SPECT was 87% (95% for detecting greater than or equal to 70% stenoses), and the normalcy rate in the low likelihood g roup was 90%. In patients completing both arbutamine and exercise stre ss testing, thallium-201 SPECT sensitivity for detecting coronary arte ry disease (greater than or equal to 50% stenosis) was 94% and 97% (p = NS), respectively. Furthermore, SPECT segmental visual score agreeme nt (defect vs. no defect) showed a concordance of 92% between arbutami ne and exercise results (kappa 0.80, p < 0.001). The stress thallium-2 01 SPECT segmental scores showed 83% exact agreement (kappa 0.69, p < 0.001), and analysis of the reversibility of segments with stress perf usion defects demonstrated 86% exact agreement (kappa 0.68, p < 0.001) . In general, side effects associated with arbutamine were well tolera ted and resolved with discontinuation of infusion. Conclusions.Arbutam ine, administered by a closed-loop feedback system was shown to be a s afe and effective pharmacologic stress agent. Arbutamine stress thalli um-201 SPECT appears to be accurate for the diagnosis of coronary arte ry disease with a diagnostic efficacy similar to that of treadmill exe rcise thallium-201 studies.