Perfusion lung scan in patients operated for transposition of the great arteries.

Fifty perfusion lung scans were performed with Tc-99m albumin microspheres in 42 patients, 15 days to 12 years after corrective surgery for transposition of the great arteries. The scan was entirely normal in nine of 42 patients. Absence of left lung perfusion was observed in three patients and hypoperfusion of the left lung in 19 patients. Segmentary zones of hypoperfusion was visualized in 13 patients either in the right or left lung. A moderate right to left shunt was observed in eight cases. The absence or decrease in left lung perfusion was due to pulmonary vein occlusion in four patients, left pulmonary artery stenosis in two patients, and preferential right blood flow in one patient. Right to left shunt was due to dehiscence of the atrial patch in four patients.