Right Ventricular Remodeling and Wall Shear Stress; 4D Flow Analysis in Repaired Tetralogy of Fallot Undergoing Transcatheter Pulmonary Valve Implantation

Using 4D Flow MRI, we evaluated right ventricular (RV) remodeling and potential exacerbating factors of pulmonary regurgitation—particularly wall shear stress (WSS)—before and after transcatheter pulmonary valve implantation (TPVI) with the Harmony TPV 25 in adult patients with repaired tetralogy of Fallot. Thirty patients who underwent TPVI, along with right heart catheterization were assessed pre- and 3 months post-TPVI using cardiac MRI (CMR) including 4D flow; 15 had follow-up at 1 year. RV end-diastolic volume index (RVEDVi) and 4D-derived regurgitant fraction (RF-4D) significantly decreased at 3 months (RVEDVi: 159.2 ± 38.7 to 107.7 ± 33.6 mL; RF-4D: 42.5 ± 11.3% to 2.2 ± 3.9%; both p < 0.001). At 1 year, 13 of 14 patients with preoperative RVEDVi < 200 mL achieved normalization. RVEDVi reduction at 3 months correlated with preoperative RF-4D, and at 1 year correlated with both preoperative RF-4D and RVEDVi. Preoperative MPA cross-sectional area correlated with RF-4D but not with mean pulmonary artery pressure. Preoperative WSS showed a biphasic pattern, increasing in early diastole due to pulmonary regurgitation, and significantly decreased post-TPVI. Early diastolic WSS pre-TPVI demonstrated a significant inverse correlation with age and MPA cross-sectional area. These findings suggest WSS appears to play a key role in pulmonary artery dilation associated with worsening pulmonary regurgitation.