Right ventricular outflow tract obstruction as a confounding factor in the assessment of the impact of pulmonary regurgitation on the right ventricular size and function in patients after repair of tetralogy of Fallot.

PURPOSE: To compare right ventricular (RV) size and function between patients with combined pulmonary regurgitation (PR) plus RV outflow tract (RVOT) obstruction (RVOTO) and patients with isolated PR. MATERIALS AND METHODS: Consecutive individuals with significant PR (PR fraction ≥ 20%) after tetralogy of Fallot (TOF) repair who underwent cardiovascular magnetic resonance (CMR) were included. Patients with additional hemodynamic abnormalities (residual ventricular septal defect, extracardiac shunt, and/or more than mild regurgitation at a valve other than the pulmonary valve) were excluded. Significant RVOTO was defined as peak gradient across RVOT ≥ 30 mmHg. RESULTS: Significant differences between patients with combined PR+RVOTO (n = 9) and isolated PR (n = 33) were observed in RV end-diastolic volume (138.6 ± 25.1 vs. 167.0 ± 34.6 mL/m(2) , P = 0.02, respectively), RV end-systolic volume (65.0 ± 9.6 vs. 92.7 ± 26.2 mL/m(2) , P = 0.003), and RV ejection fraction (RVEF) (52.8 ± 3.7 vs. 45.0 ± 6.4%, P = 0.001). Both PR and peak RVOT gradient were independent predictors of RV size. CONCLUSION: Patients with combined PR+RVOTO had smaller RV volumes and higher RVEF when compared with patients with isolated PR. The confounding effect of RVOTO on RV size and function needs to be considered in CMR studies evaluating patients after TOF repair.