Abstract 18027: Effects of Prolonged Exercise in Patients with Systemic Right Ventricles
INTRODUCTION Cardiac fatigue is described in healthy participants after ultraendurance competitions often disproportionately affecting the right ventricle. Patients with systemic right ventricles as a result of D-transposition of the great arteries (D-TGA) with an atrial switch procedure or with L-TGA provide a unique model to evaluate the effects of exercise on the right ventricle.
METHODS Eleven patients with D-TGA s/p Mustard procedure and three patients with L-TGA were recruited from our ACHD clinic. All were NYHA class I, without severe ventricular dysfunction or severe valve regurgitation. Patients were matched 2:1 with healthy controls. All participants underwent 2 days of exercise treadmill testing. Day 1: steady state (ss) exercise at ∼ 30% and ∼60% of VO2Max. Day 2: 60 minute prolonged exercise just below lactate threshold. Cardiac output was obtained with the acetylene rebreathing method. Oxygen uptake was measured using the Douglas bag method.
RESULTS Oxygen uptake (VO2), cardiac output (Qc), and stroke volume (SV) were higher in controls than patients at all levels of exercise (p<0.05, except VO2 at SS 30% Max). At SS 60% Max, VO2 (mL/kg/min) =24 ± 5.9 v 15±2.9, Qc (L/min)=14±2.9 v 8.4±1.9, SV (mL/beat)=96±22 v 75±19. Qc and SV were preserved for the duration of exercise in both groups. There was a blunted Qc /VO2 relationship with submaximal exercise in the patients that did not achieve conventional levels of statistical significance (slope=5.1± 1 v 5.9± 1.3, p=0.2). Relative heart rate increase from baseline during exercise was similar between groups.
CONCLUSIONS Patients with systemic right ventricles as a result of transposition of the great arteries have diminished cardiac output, stroke volume and oxygen uptake during submaximal exercise. However patients did not have evidence of cardiac fatigue with prolonged exercise at the lactate threshold suggesting that such exercise duration and intensity is safe, and may be effective as a training stimulus.
- © 2012 by American Heart Association, Inc.