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 perfusion single photon emission computed tomographic imaging (SPECT) for the diagnosis of vascular stenosis after coronary artery bypass grafting (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 evaluation of patients with limited exercise capacity, its value in the diagnosis of vascular stenosis after CABG has not been studied. Methods  Dobutamine (up to 40 μg/kg/min)-atropine (up to 1 mg) stress test in conjunction with myocardial perfusion SPECT imaging (²⁰¹Tl or 99m technetium sestamibi [MIBI]) was performed in 71 patients (mean age 58±9 years, 57 men) with limited exercise capacity referred for evaluation of myocardial ischemia 3.7±3.5 years after CABG. Significant vascular stenosis was defined as ≥50% luminal 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. Sensitivity, specificity, and accuracy of reversible perfusion defects at dobutamine SPECT for the overall diagnosis of vascular stenosis were 81%, confidence interval (CI) 72 to 90, 79%, CI 69 to 88, and 80%, CI 71 to 90, respectively. Significant vascular stenosis was detected in 73 arterial regions. Sensitivity, specificity, and accuracy of dobutamine 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. Patients with multivessel stenosis had a higher number of ischemic segments (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 stenosis, respectively. Significant graft stenosis was detected in 67 graft regions. Sensitivity, specificity, and accuracy of dobutamine SPECT for 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  Dobutamine stress myocardial perfusion SPECT imaging is a useful method for the diagnosis of significant vascular stenosis after CABG in patients with limited exercise capacity. Supported in part by the Department of Cardiology, Cairo University Hospital, Cairo, Egypt and by a grant from the NUFFIC, the Hague, the Netherlands.