Prolonged cardiac recovery from exercise in asymptomatic adults late after atrial correction of transposition of the great arteries: evaluation with magnetic resonance flow mapping

After atrial correction of transposition of the great arteries (TGA), dysfunction of the systemic right ventricle at rest and during exercise has been reported. Information on changes in systemic right ventricular function during recovery from exercise is lacking. This study evaluates cardiac recovery from supine exercise using magnetic resonance (MR) imaging in patients with asymptomatic TGA after atrial correction. Flow in the ascending aorta, representing stroke volume of the systemic ventricle, was assessed with MR flow mapping in 10 asymptomatic patients with atrially corrected TGA and in 12 controls at rest during exercise and an 8-minute recovery period. In response to exercise, the patients had a smaller increase in heart rate, stroke volume, and cardiac output than did controls. After exercise, no significant difference in halftime of heart rate recovery was observed (patients, 48 ± 7 seconds; controls, 39 ± 4 seconds [p >0.05]). In the patients, the time course of stroke volume recovery was significantly different (p <0.001). Stroke volume in the patients, as a percent difference from rest, remained significantly elevated, from 2.5 minutes (+16 ± 5% vs +7 ± 6%; p <0.05) to 8 minutes (+4 ± 7% vs −3 ± 5%; p <0.05) after exercise. Subsequently, cardiac output remained significantly elevated, from 4.5 minutes (+27 ± 13% vs +15 ± 11%; p <0.05) to 7 minutes (+22 ± 11% vs +12 ± 12%; p <0.05) after exercise. We conclude that heart rate recovery is within normal limits in patients with atrially corrected TGA. Furthermore, cardiac recovery from exercise, assessed with MR flow mapping, is prolonged in patients with asymptomatic TGA after atrial correction. Abnormal recovery may reflect dysfunction of the systemic right ventricle and an altered metabolic response to exercise.