Revisiting Manifestations of Dipyridamole Stress/Redistribution Tl Myocardial Perfusion Imaging in Patients with Coronary Artery Fistula: A Report of Four Cases

Received 7/16/2008; revised 9/5/2008; accepted 9/8/2008. For correspondence and reprints contact: Ming-Hsien Lin, M.D., Division of Nuclear Medicine, Taipei City Hospital Zhongxiao Branch. 87 Tonde Road, Nangang District, Taipei 115, Taiwan, Tel: (886)2-27861288 ext. 8089, Fax: (886)2-26534501, E-mail: [email protected] Previous reports stated that patients with coronary artery fistula (CAF) and angina pectoris mostly had perfusion defects on Tl-myocardial perfusion SPECT with dipyridamole stress (dipyridamole Tl-MPI). These perfusion defects were reversible or of reversed redistribution patterns, and the mechanism was generally considered as steal phenomenon. Four patients with angina pectoris and major risk factors of coronary artery disease (CAD) undergoing dipyridamole Tl-MPI and coronary angiography (CAG) in our hospital from 1995 to 1999 were found to have CAFs. The durations between the two examinations were two weeks to one year. Except one case with 50%-60% of coronary artery stenosis and CAF in the middle segment of left anterior descending artery (LAD) had perfusion defect in the apical wall of left ventricle (LV) on MPI, all others did not have corresponding perfusion defect in the coronary territories with CAF, even if concomitant coronary stenosis or double CAF was present. The prevalence of corresponding perfusion defect on dipyridamole TlMPI in patients with CAF and angina pectoris in our series is not as high as previously reported. It is not rare for a patient with concomitant CAF and coronary stenosis in the same vessel to have no corresponding perfusion defect on dipyridamole Tl-MPI. Further studies to correlate shunt ratio of CAF with manifestations of dipyridamole Tl-MPI, to characterize dipyridamole-induced hemodynamic changes of the coronary territory with CAF relative to other territories, and comparing the diagnostic performances of vasodilator versus dobutamine or exercise stress MPI for CAF may be promising.