The Impact of the Right Ventricular Outflow Tract Patch on Right Ventricular Strain in Tetralogy of Fallot: A Comparison with Valvar Pulmonary Stenosis Utilizing Cardiac Magnetic Resonance

Abstract

A non-contractile transannular patch (TAP) in the right ventricular outflow tract (RVOT) contributes to ventricular dysfunction after tetralogy of Fallot (TOF) repair. We compared regional right ventricular (RV) strain in repaired TOF with valvar pulmonary stenosis (VPS) after balloon valvuloplasty to investigate the effects of TAP. Retrospective review of 26 cardiac magnetic resonance studies of TOF (n = 13) and VPS (n = 13) subjects matched by degree and duration of pulmonary regurgitation (PR). Feature tracking strain analysis was performed. Student's t tests, Pearson correlation, and linear regression were applied. RV ejection fraction (EF) was normal and similar between TOF and VPS (60 and 65%, respectively, p = 0.8). RV 4-chamber Lagrangian longitudinal strain (RV 4ch LS) was worse in both groups compared to normals but comparable to each other: -18.2 (95% CI -3.6 to -33) for TOF and -20.2 (95% CI -12.4 to -28) for VPS, p = 0.5. RVOT LS was worse than RV 4ch LS in TOF, p = 0.05, but not in VPS, p = 0.19. There were no significant differences in RVOT strain between groups, p = 0.18. RVOT strain and RV 4ch LS correlated positively with RV EF in VPS (r = 0.72, p = 0.003 and r = 0.55, p = 0.04). PR degree correlated negatively with RVOT LS for TOF and VPS. Longitudinal strain is diminished in VPS and TOF subjects with preserved RV EF. TAP could explain worse RVOT strain in TOF. Longitudinal studies are needed to ascertain if RV strain predicts worsening of RV EF.

Keywords: Cardiac MRI; Congenital heart disease; RV function; Strain.