Response toExercise After VenousSwitchOperation for Transposition oftheGreat Arteries

Study objective: Thisstudy reports on thecardiorespirator y response tograded exercise in patients after venous switch operation fortransposition ofthegreat arteries. Design: Several small studies havedocumented a diminished exercise tolerance after Mustard repair fortransposition ofthegreat arteries; little information exists, however, aboutlong-term cardiorespirator y exercise performance inpatients whohavehadtheSenning procedure. Patients: Thisprospective study reports on theserial long-term (mean, 11±2.8years) cardiopul¬ monaryexercise performance of43patients (age, 12±3.1years) whounderwent a Senning procedure, with no significant postoperative abnormalities. Forty-three matchedhealthy chil¬ dren were also studied as a control group. Measurements andresults: Allunderwent exercise testing (Bruce protocol) withmetabolic gas exchange todetermine parameters at3 min,anaerobic threshold, similar heart rate(150 beats/min), andpeak exercise. Timeofexercise was 10.5±1.9 mininpatients and13.4±2minin control subjects (p=0.0001). Overall, patients reached 73%ofpeak oxygenuptake achieved by control subjects (32.6±5.6 vs 44.7±6mL/kg/min). Chronotropic response (188±15.7 vs 166.5±19.6 beats/min [p=0.0001]) andoxygen pulse (7.4±2.9 vs 10.7±4.2 mL/beat [p=0.0002]) were lower inpatients atpeak exercise. Patients hada greater respiratory response toexercise: bothrespiratory rateandventilatory equivalent forcarbon dioxide were significantly higher atall stages ofexercise. Exercise capacity assessed bypeak oxygenuptake was correlated withtime elapsed sincesurgical repair (r=0.48; p=0.001). Conclusions: Itisconcluded that even inasymptomatic patients, exercise endurance and respiratory response are generally altered as muchas 11±2.8yearsafter venous switch operation, although early surgical repair ispredictive ofa better long-term functional result. (CHEST 1997; 111:23-29)