We aimed to assess the haemodynamic effects of exercise training in transposition of the great arteries (TGA) patients with systemic right ventricles (SRVs). TGA patients have limited exercise tolerance and early mortality due to systemic (right) ventricular failure. Whether exercise training enhances or injures the SRV is unclear. Fourteen asymptomatic patients (34± 10 years) with TGA and SRV were enrolled in a 12week exercise training programme (moderate and high-intensity workouts). Controls were matched on age, gender, BMI and physical activity. Exercise testing pre- and post- training included: (a) submaximal and peak; (b) prolonged (60min) submaximal endurance and (c) high-intensity intervals. Oxygen uptake (V˙O2<inf>;</inf> Douglas bag technique), cardiac output (Q˙c, foreign-gas rebreathing), ventricular function (echocardiography and cardiac MRI) and serum biomarkers were assessed. TGA patients had lower peak V˙O2, Q˙c, and stroke volume (SV), a blunted Q˙c/V˙O2 slope, and diminished SV response to exercise (SV increase from rest: TGA=15.2%, controls=68.9%, P<0.001) compared with controls. After training, TGA patients increased peak V˙O2 by 6±8.5%, similar to controls (interaction P=0.24). The magnitude of SV reserve on initial testing correlated with Q˙c training response (r=0.58, P=0.047), though overall, no change in peak Q˙c was observed. High-sensitivity troponin T (hs-TnT) and N-terminal prohormone of brain naturetic peptide (NT pro-BNP) were low and did not change with acute exercise or after training. Our data show that TGA patients with SRVs in this study safely participated in exercise training and improved peak V˙O2. Neither prolonged submaximal exercise, nor high-intensity intervals, nor short-term exercise training seem to injure the systemic right ventricle.
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