Pulmonary artery remodeling and wall shear stress in repaired tetralogy of fallot: insights from 4D flow MRI before and after transcatheter pulmonary valve implantation

To investigate hemodynamic factors associated with pulmonary artery (PA) remodeling in repaired tetralogy of Fallot (rTOF), focusing on wall shear stress (WSS) and pulmonary regurgitation (PR), and to assess pre- and post-procedural changes following transcatheter pulmonary valve implantation (TPVI) using 4D flow MRI. Thirty rTOF patients undergoing TPVI were analyzed using pre- and 3-month post-procedural 4D flow MRI. Regurgitant fraction (RF-4D), ventricular parameters, and WSS along the main pulmonary artery (MPA) were quantified. Pre-TPVI, RF-4D correlated with MPA dilation (r = 0.567, p = 0.001), whereas no association was observed with mean pulmonary arterial pressure. Both systolic and diastolic WSS showed significant negative correlations with MPA area. Multivariable analysis demonstrated that RF-4D (β = 11.52, p < 0.001) and diastolic WSS (β = -0.54, p = 0.003) were independently associated with MPA dilation, while age was not significant. Post-TPVI, RF-4D decreased markedly with right ventricular reverse remodeling. Early diastolic WSS significantly decreased, while systolic WSS remained unchanged, resulting in resolution of the biphasic WSS pattern. In rTOF, pulmonary artery dilation was more strongly associated with pulmonary regurgitation-derived flow metrics than with pressure, suggesting a dominant role of flow-related hemodynamic stress. Diastolic WSS decreased after TPVI in parallel with reduction of PR and may reflect the stage of vascular remodeling. These findings suggest that WSS may serve as a mechanistic marker of pulmonary artery remodeling and may provide additional value for risk stratification in patients with progressive pulmonary regurgitation and PA dilation.