Usefulness of magnetic resonance imaging for evaluating great-vessel anatomy after arterial switch operation for D-transposition of the great arteries.

Magnetic resonance imaging (MRI) produces high-resolution images of great-vessel anatomy in pediatric patients. In this study seven patients, aged 6 to 27 months were evaluated by using gated MRI and two-dimensional echocardiography 4 to 26 months after arterial switch operation for D-transposition of the great arteries. Measurements were taken at the right and left ventricular outflow tracts, beneath the semilunar valves, at the midaortic sinuses, at the anastomotic sites of the main pulmonary artery and the aorta, at the origin of the branch pulmonary arteries, and at the distal pulmonary arteries 1 cm beyond the bifurcation. Concordant results were obtained with both imaging techniques from all sides with the exception of the left pulmonary artery and the right pulmonary artery. With MRI, four patients had significant narrowing at the right pulmonary artery origin and six patients had narrowing at the left pulmonary artery origin. With two-dimensional echocardiogram, two patients had narrowing at the right pulmonary artery origin and four patients had narrowing at the left pulmonary artery origin. The measured pulmonary artery intraluminal diameters in these patients were consistently smaller when assessed by MRI versus two-dimensional echocardiography. To verify these results, five of seven patients underwent cardiac catheterization to provide physiologic correlation before reoperation; the MRI results were found to be significantly closer to the actual catheterization measurements. We conclude that MRI is a sensitive imaging technique for evaluation of great-vessel anatomy in patients after arterial switch operation for D-transposition of the great arteries. It is particularly useful in the evaluation of the branch pulmonary artery anatomy.