Evaluation of ²⁰¹Tl SPET myocardial perfusion imaging in the detection of coronary artery disease after orthotopic heart transplantation

Accelerated coronary artery disease is a common complication following orthotopic cardiac transplantation. The relationship between acute rejection and accelerated coronary artery disease remains unclear. While thallium-201 (²⁰¹Tl) imaging has been advocated in the diagnosis of post-transplant coronary arteriopathy, other investigators have found little role for this technique in the evaluation of such patients. We undertook a retrospective review of 13 stress/rest (10 exercise, 2 dobutamine, 1 dipyridamole) and 2 rest/rest ²⁰¹Tl single photon emission tomographic (SPET) imaging studies performed in seven patients post-cardiac transplantation (mean duration post transplantation = 2.5 years). Four of these patients had serial studies with an average interval between studies of 8.3 months (range 3-14 months). Coronary angiography was performed within 12 months of each ²⁰¹Tl study (mean = 4.2 months). Using the coronary angiographic diagnostic criterion of ≥ 50% stenosis in one or more vessels, one or more fixed or reversible segmental defects were found on ²⁰¹Tl imaging with a sensitivity of 78% and specificity of 33%. When the angiographic criterion of > 70% stenosis in one or more vessels was used the sensitivity increased to 100%, and where reversible segments were diagnostic the sensitivity was 67% and the specificity ranged from 42 to 58%. Although based on a small sample of patients, these results suggest that use of appropriate test methods and interpretive criteria may improve the utility of ²⁰¹Tl SPET myocardial imaging in the diagnosis of coronary artery disease in cardiac transplant patients. Limited specificity may reflect associated pathological processes in these patients, including rejection, oedema and focal inflammation.