A Smaller Right Ventricle Results in Poorer Exercise Performance in Adolescents After Surgical Repair of Tetralogy of Fallot

BackgroundChronic pulmonary valve insufficiency frequently results in right ventricular (RV) dilatation and dysfunction in surgically repaired tetralogy of Fallot (rTOF). Correlations between peak exercise performance and progression of RV remodeling in rTOF remain elusive. MethodsPatients with rTOF were reviewed with cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR). Peak and submaximal CPET parameters were obtained. Both RV and left ventricular (LV) volume were measured in end-systole (RVESV and LVESV, respectively) and end-diastole (LVEDV and RVEDV, respectively). Stroke volume (SV), ejection fraction (EF), and pulmonary regurgitant fraction (RF) were calculated. ResultsThirty-seven patients (17 {+/-} 5 years; 22 females; 5 with pulmonary atresia and 2 with absent pulmonary valve) were studied. Pulmonary RF was 28.3 {+/-} 13.4%. Indexed RVEDV was 132 {+/-} 33 mL/m2. Ejection fraction of RV and LV was 50.3 {+/-} 7.8% and 59.1 {+/-} 6.1%, respectively. Peak oxygen consumption (pVO2) was 71 {+/-} 16% of predicted maximum value. A strong positive correlation was noted between CMR data including RVEDV, RVSV and LVSV, and pVO2. Higher RVEDV was correlated with higher RVSV and LVSV and higher pVO2, whereas lower RVEDV was associated with lower RVSV and LVSV and lower pVO2. ConclusionIn rTOF, smaller RV resulted in reduced SV of both ventricles and significantly lower pVO2, whereas larger RV provided higher SV and higher pVO2 regardless of RVEF or RF. Smaller RV in rTOF may represent a unique pathological entity responsible for reduced exercise performance, which requires special consideration when determining further surgical interventions. Clinical Perspective What is New?We characterized a novel clinical entity after surgical repair of tetralogy of Fallot (TOF) with a relatively small right ventricle (RV) and decreased exercise performance. It is likely due to limited RV stroke volume adjustment in response to peak exercise affecting left ventricular (LV) stroke volume. Although the pathogenesis of this smaller RV remains undetermined, our results shed light on the diverse clinical phenotypes after surgical repair of TOF. What are the Clinical Implications?Pulmonary valve replacement (PVR) is a treatment option for progressive RV dilatation and/or symptoms of exercise intolerance related to persistent pulmonary valve insufficiency in repaired TOF. Our data demonstrated that poor exercise performance was more frequently associated with a smaller RV size rather than dilated RV. Indication for PVR in repaired TOF needs to be carefully assessed in symptomatic patients with non-enlarged RV.