MRI of pulmonary arteries in follow-up after arterial-switch-operation (ASO) for transposition of great arteries (d-TGA)

Purpose: To determine the value of MR1 in postoperative evaluation of patients with arterial-switch-ope ration (ASO) for d-TGA. Material and Methods: 14 consecutive patients with d-TGA and ASO were examined with MRI in addition to ultrasound because the acoustic window in echocardiography was insufficient. Nine patients had a pulmonary-artery-bifurcation anterior to the aortic root (group 1), and five (group 2) laterally (two of them left, three of them right). MRI was performed in six patients as contrast-enhanced MR-angiography, in 8 patients as native examination. Diameters of pulmonary arteries were measured in two perpendicular views at the origin and in two further locations each with a distance of one cm. Results: One patient showed a supravalvular pulmonary artery stenosis with subsequent pulmonary artery aneurysm, which had not been detected in echocardiography. This patient showed only indirect signs of pulmonary artery stenosis in echocardiography. Compared to group 1, pulmonary arteries in group 2 generally had greater diameters. Those pulmonary arteries in Group 2 which cross the mediastinum underneath the aortic arch had lower diameters compared to the pulmonary artery positioned on the other side. In group 1, the left-sided pulmonary artery had lower diameters than the right-sided pulmonary arteries. It seems remarkable that the narrowing of pulmonary arteries is associated with a flattening of the transversal vessel diameter. Conclusion: Narrowing of pulmonary arteries after ASO is associated with oval vessel diameters. Therefore, multiplanar diagnostic methods are necessary. MRI meets this prerequisite and is therefore advantageous to echocardiography in follow-up examinations at patients with ASO for d-TGA. Special attention should be focused on the main pulmonary artery, on the left pulmonary artery in patients with preaortic pulmonary artery bifurcation as well as on the pulmonary artery which crosses the mediastinum in patients with laterally placed pulmonary artery bifurcation. Angiography should only be performed when intervention is planned.