Accuracy of dobutamine tetrofosmin myocardial perfusion imaging for the noninvasive diagnosis of transplant coronary artery stenosis

Background: Exercise stress myocardial perfusion scintigraphy has been used for the diagnosis of transplant coronary artery stenosis (TCAS) in cardiac allograft recipients. However, the role of pharmacologic stress myocardial perfusion imaging has not been evaluated. Aim of the study is to assess th e accuracy of dobutamine stress 99m technetium tetrofosmin myocardial perfu sion imaging for the diagnosis of TCAS in heart transplant recipients. Patients and methods: We studied 50 patients (age 56 +/- 8 year, 45 men) at a mean of 6.4 +/- 2.8 years after cardiac transplant with dobutamine (up t o 40 ig/kg/min) stress 99m technetium tetrofosmin SPECT. Resting images wer e acquired 24 hours after the stress study. Significant TCAS was defined as greater than or equal to 50% luminal diameter stenosis by coronary angiogr aphy. Results: Significant TCAS was detected in 30 patients (60%). Myocardial per fusion abnormalities (reversible and/or fixed defects) were detected in 27 of the 30 patients with and in 9 of the 20 patients without significant TCA S (sensitivity = 90%, CI 82-98, specificity = 55% CI 41-69, positive predic tive value = 75%, CI 63-87, negative predictive value = 79%, CI 67-90 and a ccuracy = 76%, CI 64-88). Patients with multivessel TCAS had a larger stres s perfusion defect score (5.6 +/- 3.1 vs 3.2 +/- 2.4, p < 0.05) compared to patients with single vessel TCAS. Among patients with abnormal perfusion w ho had no significant TCAS, 2 had lesions <50%, 2 had luminal irregularitie s and 5 had no abnormalities at angiography. Therefore specificity was 62% (8/13) in patients without any detectable angiographic abnormalities. Conclusions: Dobutamine stress tetrofosmin myocardial perfusion imaging is a highly sensitive method for the detection of TCAS in recipients of cardia c allografts, The high negative predictive value of the test indicates that patients who demonstrate normal perfusion by this method may be excluded f rom further invasive studies.