Dissertation Date: November 11, 2026
Pediatric pulmonary vein stenosis (PVS) is a progressive disease that has a ~40% 2-year untreated survival rate in children under 2 years old (McLennan et al. 2021). Stenting is a common treatment, but restenosis occurs in >50% of cases at 6 months and 5-year survival is <50%. Adverse mechanical stimuli in the form of wall shear stress (WSS) have been implicated in restenosis in other vasculature and age groups. Unfortunately, there are no studies that include stent geometry, physiologic boundary conditions, and local blood flow patterns within stented pulmonary veins (PV). Hence, it is unknown whether optimizing mechanical stimuli after stenting will benefit PVS outcomes. The objective of this work was therefore to characterize stent-induced changes in WSS indices from data of patients treated for PVS using computational fluid dynamics modeling and investigate theoretical stent design changes that could mitigate adverse WSS indices.
Patient-specific stented PV geometries were reconstructed from computed tomography and included the left atrium, PV and branches influencing local flow patterns. The make and model of stents used for each patient were then virtually implemented. PV-specific boundary layer meshes were created to resolve complex flow features near stent struts. Inlet boundary conditions including Doppler-based velocities and pressure were tuned to available clinical data. WSS indices of time-average WSS (TAWSS) and oscillatory shear index (OSI) were calculated for each stented and unstented (control) PV. Ensemble-averaged TAWSS and OSI for stented and control PVs were compared using the unequal variances two-sample Student’s t-test (Welch’s t-test), identifying several regions where results of WSS indices were statistically different between stented and control vessels (P < 0.05). In addition, alternative stent designs focusing on stent length, radial strut thickness, and number of circumferential repeating units (thereby mimicking a common clinical practice of overexpansion) were created and likewise assessed with regard to TAWSS and OSI.
The local design of stent linkages affects blood flow patterns within intrastent regions, giving rise to converging velocity vectors where strut distances narrow and diverging velocity vectors where strut distances widen. Resulting stent-induced changes in TAWSS and OSI were most pronounced near the atrial ostia where the PVs meet the left atrium. Nearly all stents also extended to some degree into the left atrium, which directs and constrains blood flow as it exits stented PVs. Among alternative stent designs, decreased radial strut thickness decreased PV pressure gradient and minimized adverse WSS indices (i.e., low TAWSS and high OSI). Results from this work provide insight into stent-induced changes in WSS indices of patients treated for PVS and their potential contributors to restenosis, motivated by the goal of improving long-term outcomes for patients treated for PVS by stenting.
