Turbulent kinetic energy in the right ventricle: Potential MR marker for risk stratification of adults with repaired Tetralogy of Fallot

PurposeTo assess right ventricular (RV) turbulent kinetic energy (TKE) in patients with repaired Tetralogy of Fallot (rToF) and a spectrum of pulmonary regurgitation (PR), as well as to investigate the relationship between these 4D flow markers and RV remodeling. Materials and MethodsSeventeen patients with rToF and 10 healthy controls were included in the study. Patients were divided into two groups based on PR fraction: one lower PR fraction group (11%) and one higher PR fraction group (>11%). Field strength/sequences: 3D cine phase contrast (4D flow), 2D cine phase contrast (2D flow), and balanced steady-state free precession (bSSFP) at 1.5T. Assessment: The RV volume was segmented in the morphologic short-axis images and TKE parameters were computed inside the segmented RV volume throughout diastole. Statistical tests: One-way analysis of variance with Bonferroni post-hoc test; unpaired t-test; Pearson correlation coefficients; simple and stepwise multiple regression models; intraclass correlation coefficient (ICC). ResultsThe higher PR fraction group had more remodeled RVs (14025 vs. 10722 [lower PR fraction, P < 0.01] and 9315ml/m(2) [healthy, P < 0.001] for RV end-diastolic volume index [RVEDVI]) and higher TKE values (5.953.15 vs. 2.23 +/- 0.81 [lower PR fraction, P < 0.01] and 1.91 +/- 0.78 mJ [healthy, P < 0.001] for Peak Total RV TKE). Multiple regression analysis between RVEDVI and 4D/2D flow parameters showed that Peak Total RV TKE was the strongest predictor of RVEDVI (R-2=0.47, P=0.002). ConclusionThe 4D flow-specific TKE markers showed a slightly stronger association with RV remodeling than conventional 2D flow PR parameters. These results suggest novel hemodynamic aspects of PR in the development of late complications after ToF repair. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1043-1053.