Refining the assessment of pulmonary regurgitation in adults after tetralogy of Fallot repair: should we be measuring regurgitant fraction or regurgitant volume?

AIMS: Pulmonary regurgitation (PR) is an important determinant of outcome after tetralogy of Fallot (TOF) repair. The physiologic impact of PR on the right ventricle remains incompletely understood. We hypothesized that a volumetric expression of PR would be a better measure of ventricular preload and a more accurate reflection of degree of insufficiency. METHODS AND
RESULTS: Patients (n = 64) with magnetic resonance imaging after TOF repair were identified. PR was quantified using: (i) phase contrast (PC) analysis of main pulmonary artery flow and (ii) differential right and left ventricular stroke volumes. PR was expressed as a volume (PR(volume)) and percentage of total forward flow (PR(fraction)). The median PC(PR volume) was 19 mL/m(2) (range 0-63 mL/m(2)) and PC(PR fraction) was 29% (range 0-58%). PR(fraction) was found to be highly variable in terms of absolute PR(volume). In those with significant PR, PR(volume) was better than PR(fraction) for the identification of severe RV dilation (receiver-operator curve area: 0.83 vs. 0.71, P = 0.003). PR(volume) using PC analysis was better at differentiating moderate from severe RV dilation (P = 0.005) as compared with PR(fraction) (P = 0.064).
CONCLUSION: PR(volume) and PR(fraction) are not interchangeable. PR(volume) may be a more accurate reflection of RV preload and may better represent physiologically significant PR as compared with PR(fraction).