Pulmonary stenosis is the most frequent problem after arterial switch operation for TGA. We experienced four cases of late severe pulmonary stenosis out of twelve patients. All four had supravalvular stenosis either at anastomotic site or at previously banded segment. One patient had associated valvular stenosis and another had bilateral branch stenosis. It is possible that valvular stenosis was due to retraction of equine pericardial patch and branch stenosis was due to overdistension. All four cases were successfully reoperated on 13∼39 months after switch operation. To prevent late pulmonary stenosis, we now alter technique of switch operation in two points. First, the great arteries are anastomosed with interrupted U-shaped sutures from outside of the vessels in whole circumference. Second, both coronary arteries are transferred with punched-out method to save tissue of Valsalva sinus, and the defects are closed with autologous pericardial patch.

Obstruction of right ventricle-pulmonary artery bioprosthetic valved conduits can result from valvular degeneration and calcification or neointimal peel formation. From 1968 through 1989, 38 patients underwent repair of congenital heart malformation with a porcine xenograft extracardiac valved conduits from right ventricle to pulmonary artery. Of 27 patients who survived after initial repair, 14 patients (8 males and 6 females) were reoperated for conduit obstructions. Ages of patients at the reoperation ranged 5 to 20yr (mean age 11.8±3.6yr) and the interval between initial repair and reoperation ranged 3 to 9yr (mean 6.6±1.7yr). The obstructed conduits were replaced with mechanical valved conduits (4 patients), nonvalved conduits (7 patients) or outflow patches (3 patients). In a half of patients, obstructions occured at multiple levels within the conduits. Obstructions mainly resulted from valvular degeneration, neointimal peel formation and anastomotic narrowings. There was no operative death but one late death due to the infective endocarditis. The systolic pressure ratio of right ventricle to left ventricle (or aorta) decreased from 0.81±0.13 preoperatively to 0.48±0.10 postoperatively. From our experience, it is recommended to use adequate sized bioprosthetic valued conduits for patients' body weight at the initial repair and replace obstructed conduits to the large sized nonvalved conduit at reoperation if possible.