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 (PRvolume) and percentage of total forward flow (PRfraction). The median PCPR volume was 19 mL/m2 (range 0–63 mL/m2) and PCPR fraction was 29% (range 0–58%). PRfraction was found to be highly variable in terms of absolute PRvolume. In those with significant PR, PRvolume was better than PRfraction for the identification of severe RV dilation (receiver-operator curve area: 0.83 vs. 0.71, P = 0.003). PRvolume using PC analysis was better at differentiating moderate from severe RV dilation ( P = 0.005) as compared with PRfraction ( P = 0.064). Conclusion PRvolume and PRfraction are not interchangeable. PRvolume may be a more accurate reflection of RV preload and may better represent physiologically significant PR as compared with PRfraction.