Smaller Right Ventricle Results in Poorer Exercise Performance in Young Patients With Repaired Tetralogy of Fallot

BACKGROUND: Severe right ventricular (RV) dilatation and exercise intolerance are considered indications for pulmonary valve replacement in surgically repaired tetralogy of Fallot (rTOF). METHODS AND RESULTS: Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) were performed in rTOF patients with pulmonary insufficiency (PI). Oxygen pulse (OP), calculated as oxygen consumption (V̇O2)/heart rate, was used as a surrogate of stroke volume (SV). Correlations between CPET and CMR measures were investigated. In all, 37 patients (mean [±SD] age 17±5 years; 14 males) were examined. Peak V̇O2/kg was approximately 70% of predicted value. The pulmonary regurgitant fraction (PRF) was 28.3±13.4%. Body surface area (BSA)-indexed RV end-diastolic volume (RVEDVi) and RVSV (RVSVi) were 127±28 and 65±16 mL/m2, respectively. RV and left ventricular (LV) ejection fractions were 50.3±7.8% and 59.1±6.1%, respectively. A strong positive correlation was noted between RV end-diastolic volume and RVSV (P<0.0001), RVSV and LVSV (P<0.0001), and RVEDVi and peak OP/BSA (P=0.0004). Larger RVEDVi was correlated with better exercise performance, whereas smaller RVEDVi was correlated with worse exercise performance. RVEDVi was larger in male than female rTOF patients despite comparable PRF, RVSVi, LVEDVi, and BSA-indexed LVSV. CONCLUSIONS: A smaller RV was associated with worse exercise performance, indicating exercise intolerance is independent of RV dilatation in young rTOF with PI and represents a unique pathological entity responsible for reduced exercise performance.