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Objective Chronic pulmonary regurgitation (PR) has deleterious effects on right ventricular (RV) function in repaired tetralogy of Fallot (ToF). However, there are little data regarding right ventricular outflow tract (RVOT) contractile dysfunction in response to chronic PR and on both RV and LV volumes and function. Methods We retrospectively identified consecutive patients with PR who were referred for magnetic resonance imaging quantification of "free PR" detected on echocardiography between 2003 and 2008. Patients had ToF and a transannular patch procedure (n = 30, 25.1 ± 1.2 years) or PR resulting from valvar pulmonary stenosis treated with surgical or percutaneous valvotomy (n = 30, 26.6 ± 1.8 years). Results The ToF and the PS groups were well matched for age at scan, age at repair surgery in ToF or initial valvotomy in PS, duration of exposure to PR, body surface area, heart rate, PR fraction, net forward pulmonary artery flow, and main and branch pulmonary artery dimensions. Severe PR fractions were identified in both groups (ToF: 40% ± 1% vs PS: 37% ± 2%, P = .2). Indexed RV and LV end-diastolic volumes were similar for both ToF and PS groups (RV end-diastolic volume index: 137 ± 6 mL/m 2 vs 128 ± 5 mL/m 2 , P = .2, and LV end-diastolic volume index: 72 ± 2 mL/m 2 vs 67 ± 2 mL/m 2 , P = .1, respectively). RV mass was also similar between groups (95 ± 5 g vs 81 ± 6 g, respectively, P = .08). However, indexed RV and LV end-systolic volumes were consistently higher in ToF when compared with PS (RV end-systolic volume index: 70 ± 5 mL/m 2 vs 54 ± 3 mL/m 2 , P 01, and LV end-systolic volume index: 29 ± 1 mL/m 2 vs 22 ± 1 mL/m 2 , P 01, respectively). These changes were reflected in lower biventricular systolic function in patients with ToF when compared with PS (RV ejection fraction: 52% ± 1.5% vs 59% ± 1%, P 001, and LV ejection fraction: 61% ± 1% vs 67 ± 1%, P 001, respectively). Although RV transannular plane systolic excursion was not significantly different between the groups ( P = .86), the RV outflow tract was considered contractile in only 50% of patients with ToF compared with 93% of patients with PS ( P = .0004). RV volumes and function were similar when only patients with contractile RV outflow tracts were compared. Conclusions RV outflow tract patch dysfunction in repaired ToF is responsible for higher end-systolic volumes and thus lower global measures of ventricular systolic function. These findings were not evident in cases of PS treated with valvotomy with comparable amount of PR. These observations highlight the importance of the initial repair surgery in ToF for late outcomes.