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

PURPOSE: 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.

METHODS

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 (WSSsteady), time-averaged WSS (taWSS), WSS in systole (WSSsystole), and WSS in diastole (WSSdiastole), 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).

RESULTS

22 patients met the inclusion criteria. Several focal hemodynamic metrics in the main and branch PAs, including WSSsteady, taWSS, WSSsystole, WSSdiastole, and OSI were associated with RV measurements at follow-up, including RVEDVi, RVESVi, and RVSVi. LPA WSSsteady,avg, RPA WSSsteady,peak, whole vessel OSIavg, and MPA OSIavg were associated with likelihood of PVR.

CONCLUSION

CFD-derived hemodynamic variables in the PAs of rToF patients are associated with both PVR and RV remodeling.