Cardiorespiratory response to exercise after venous switch operation for transposition of the great arteries

Study objective: This study reports on the cardiorespiratory response to graded exercise in patients after venous switch operation for transposition of the great arteries. Design: Several small studies have documented a diminished exercise tolerance after Mustard repair for transposition of the great arteries; little information exists, however, about long-term cardiorespiratory exercise performance in patients who have had the Senning procedure. Patients: This prospective study reports on the serial long-term (mean, 11+/-2.8 years) cardiopulmonary exercise performance of 43 patients (age, 12+/-3.1 years) who underwent a Senning procedure, with no significant postoperative abnormalities. Forty-three matched healthy children were also studied as a control group. Measurements and results: All underwent exercise testing (Bruce protocol) with metabolic gas exchange to determine parameters at 3 min, anaerobic threshold, similar heart rate (150 beats/min), and peak exercise. Time of exercise was 10.5+/-1.9 min in patients and 13.4+/-2 min in control subjects (p=0.0001). Overall, patients reached 73% of peak oxygen uptake achieved by control subjects (32.6+/-5.8 vs 44.7+/-6 mL/kg/min). Chronotropic response (188+/-15.7 vs 166.5+/-19.6 heats/min [p=0.0001]) and oxygen pulse (7.4+/-2.9 vs 10.7+/-4.2 mI/beat [p=0.0002]) were lower in patients at peak exercise. Patients had a greater respiratory response to exercise: both respiratory rate and ventilatory equivalent for carbon dioxide were significantly higher at all stages of exercise. Exercise capacity assessed by peak oxygen uptake was correlated with time elapsed since surgical repair (r=0.48; p=0.001). Conclusions: It is concluded that even in, asymptomatic patients, exercise endurance and respiratory response are generally altered as much as 11+/-2.8 years after venous switch operation, although early surgical repair is predictive of a better long-term functional result.