DOBUTAMINE-ATROPINE STRESS MYOCARDIAL PERFUSION SPECT IMAGING IN THE DIAGNOSIS OF GRAFT STENOSIS AFTER CORONARY-ARTERY BYPASS-GRAFTING

Objective. To assess the accuracy of dobutamine stress myocardial perf usion single photon emission computed tomographic imaging (SPECT) for the diagnosis of vascular stenosis after coronary artery bypass grafti ng (CABG). Background. Exercise thallium scintigraphy is a clinically useful method for the diagnosis of graft stenosis after CABG, Although dobutamine perfusion scintigraphy is an alternative method for the ev aluation of patients with limited exercise capacity, its value in the diagnosis of vascular stenosis after CABG has not been studied. Method s. Dobutamine (up to 40 mu g/kg/min)-atropine (up to 1 mg) stress test in conjunction with myocardial perfusion SPECT imaging (Tl-201 or 99m technetium sestamibi [MIBI]) was performed in 71 patients (mean age 5 8 +/- 9 years, 57 men) with limited exercise capacity referred for eva luation of myocardial ischemia 3.7 +/- 3.5 years after CABG, Significa nt vascular stenosis was defined as greater than or equal to 50% lumin al diameter stenosis of a graft or a native nongrafted coronary artery and was predicted on the basis of reversible perfusion abnormalities. Results. Significant vascular stenosis was detected in 52 patients. S ensitivity, specificity, and accuracy of reversible perfusion defects at dobutamine SPECT for the overall diagnosis of vascular stenosis wer e 81%, confidence interval (CI) 72 to 90, 79%, CI 69 to 88, and 80%, C I 71 to 90, respectively. Significant vascular stenosis was detected i n 73 arterial regions, Sensitivity, specificity, and accuracy of dobut amine SPECT for the diagnosis of regional vascular stenosis were 66%, CI 58 to 74, 83%, CI 76 to 89, and 74%, CI 67 to 81, respectively. Pat ients with multivessel stenosis had a higher number of ischemic segmen ts (1.6 +/- 1.3 vs 1 +/- 1, P <.05) and ischemic perfusion score (3.2 +/- 2.7 vs 2.2 +/- 2.3, P <.05) than patients with single-vessel steno sis, respectively, Significant graft stenosis was detected in 67 graft regions. Sensitivity, specificity, and accuracy of dobutamine SPECT f or the diagnosis of regional graft stenosis were 64%, CI 56 to 73, 85% , CI 78 to 91, and 74%, CI 66 to 82, respectively. Conclusion. Dobutam ine stress myocardial perfusion SPECT imaging is a useful method for t he diagnosis of significant vascular stenosis after CABG in patients w ith limited exercise capacity.