Aims: This study compares the functional outcome and cardiorespiratory response to exercise, in patients who have undergone arterial switch for transposition of the great arteries, with normal controls and patients who have undergone atrial switch operation.
Methods and results: Fifteen patients who had undergone arterial switch (mean age 8.5+/-2.9 years) were compared to 32 patients who had undergone atrial switch (9.2+/-1.8 years) and 27 normal controls (8.5+/-2.1 years). Exercise testing was performed on a treadmill and gas exchange measured breath-by-breath. Aerobic capacity, assessed by determination of the ventilatory anaerobic threshold, averaged 91+/-7.8% of normal (95% confidence limits: 92-108%) for arterial switch and 75.1+/-13.1% for atrial switch (P<0.001 patients vs normals). Aerobic exercise function was evaluated by calculation of the slope of oxygen uptake vs exercise intensity. The mean value for this slope was 2.0+/-0.25 for arterial switch, 2.5+/-0.46 for normals and 1.7+/-0.80 for atrial switch (P<0.05; patients vs normals). Efficiency of the pulmonary gas exchange was assessed by calculation of the slope of ventilation vs carbon dioxide output during exercise. This averaged 38.7+/-14.7 for arterial switch, 48.1+/-14.1 for atrial switch and 30.3+/-7.6 for normals (P<0.001; patients vs normals).
Conclusion: Cardiorespiratory exercise function is at, or slightly below, the lower limit of normal in patients with arterial switch, while the lowest values were observed for those who had undergone atrial switch.