Exercise performance after the arterial switch operation for D-transposition of the great arteries

Early- and intermediate-term results of the arterial switch operation for D-transposition of the great arteries (D-TGA) are encouraging. However, questions remain about the long-term outcome for these patients, especially with regard to exercise performance. Preliminary studies have demonstrated normal endurance time on treadmills. However, data regarding aerobic capacity and cardiopulmonary function are lacking. We report the cardiopulmonary performance of 22 school-age patients with D-TGA who underwent the arterial switch operation. Outcome variables included maximal oxygen consumption (VO2), maximal cardiac index, and peak heart rate. Patient and procedure-related variables were assessed for their association with outcome variables using linear and logistic regression. The mean values of maximal VO2 (113 +/- 19% predicted) and maximal cardiac index (96 +/- 18% predicted) were within normal limits for the pediatric population. Although the mean peak heart rate for the entire group (184 +/- 14 beats/min) was within normal limits, there were 7 subjects (32%) with chronotropic impairment. Significant ST-segment depression was seen in 2 subjects (9%). In regression analysis, surgery subsequent to the arterial switch was associated with lower maximal cardiac index (p = 0.01). Other variables were not significantly associated with maximal VO2, maximal cardiac index, and peak heart rate. In particular, chronotropic impairment was not significantly associated with maximal VO2 or maximal cardiac index. These findings demonstrate that cardiopulmonary performance during exercise is excellent after the arterial switch operation. The finding of ST-segment depression in some subjects supports the role of formal exercise testing in those patients participating in vigorous athletic activities.