OBJECTIVE: The main cause of long-term morbidity and mortality after a successful arterial switch operation for transposition of the great arteries is complications at the ostial segments, proximal segments, or both of the retransferred coronary arteries. The purpose of this study was to investigate the clinical usefulness of multislice computed tomographic angiography in detecting ostial and proximal coronary lesions in children having undergone the arterial switch operation for transposition of the great arteries. METHODS: Forty-nine children (aged 8.5 +/- 3.9 years) operated on for transposition of the great arteries with the arterial switch operation (follow-up, 8.3 +/- 3.6 years) underwent systematic selective conventional and multislice computed tomographic angiography. The ability of multislice computed tomography in detecting stenosis and other modifications of the coronary arteries' course was analyzed by 2 independent investigators. RESULTS: Multislice computed tomography, as compared with selective conventional coronary angiography, permitted assessment of ostial and proximal coronary segments in every patient. It correctly detected the 4 (8.1%) patients with significant coronary lesions (1 with ostial and 3 with proximal coronary stenosis) that had been identified by means of conventional angiography. Multislice computed tomography clearly showed an abnormal course of the coronary artery between the great arteries with compression of the ostial (1 patient) and proximal (3 patients) segments of the retransferred coronary arteries. CONCLUSION: These results indicate that multislice computed tomographic angiography is fully accurate in detecting ostial coronary artery stenoses, proximal coronary artery stenoses, or both in pediatric patients having undergone the arterial switch operation for transposition of the great arteries. Our results suggest that multislice computed tomography could be used as a screening technique for detecting coronary complications in the follow-up of the arterial switch operation before having recourse to conventional angiography.