Pulmonary Artery Shear Stress and Oscillatory Shear Index are Associated with Right Ventricular Remodeling in Repaired Tetralogy of Fallot.

Abstract

Right ventricular (RV) remodeling in repaired tetralogy of Fallot (rToF) is a multifactorial process that may be affected by downstream hemodynamics. We therefore sought to characterize hemodynamics in the pulmonary arteries (PAs) of rToF patients using cardiovascular magnetic resonance (CMR)-derived computational fluid dynamics (CFD) and to study these variables in association with RV measurements at follow-up. We selected patients with two CMRs who had magnetic resonance angiography (MRA) performed at baseline. The PA was segmented from the main PA (MPA) through the first bifurcation of the left PA (LPA) and right PA (RPA). Both steady and pulsatile simulations were performed. For each vessel, we calculated curvature, tortuosity, and both average (avg) and peak steady WSS (WSS_steady), time-averaged WSS (taWSS), WSS in systole (WSS_systole), and WSS in diastole (WSS_diastole), as well as oscillatory shear index (OSI). We studied these variables in association with RV metrics at follow-up including: RV end-diastolic volume index (RVEDVi), RV end-systolic volume index (RVESVi), RV stroke volume index (RVSVi), and RV ejection fraction (RVEF), as well as the outcome of pulmonic valve replacement (PVR). 22 patients met the inclusion criteria. Several focal hemodynamic metrics in the main and branch PAs, including WSS_steady, taWSS, WSS_systole, WSS_diastole, and OSI were associated with RV measurements at follow-up, including RVEDVi, RVESVi, and RVSVi. LPA WSS_steady,avg, RPA WSS_steady,peak, whole vessel OSI_avg, and MPA OSI_avg were associated with likelihood of PVR. CFD-derived hemodynamic variables in the PAs of rToF patients are associated with both PVR and RV remodeling.