Patient-Specific Computational Flow Simulation Reveals Adverse Hemodynamic Factors Associated With Occlusion of Directional Branches After Fenestrated-Branched Endovascular Aneurysm Repair.

BACKGROUND: Fenestrated and branched endovascular aneurysm repair can be complicated by branch vessel occlusion in the absence of structural stenosis. We hypothesized that computational flow simulation could identify adverse hemodynamic features associated with postfenestrated and branched endovascular aneurysm repair branch occlusion.

METHODS: Patients undergoing 4-vessel fenestrated and branched endovascular aneurysm repair for Extent II to IV thoracoabdominal aortic aneurysms were retrospectively reviewed. Branches that occluded without identifiable kinking or stenosis on computed tomography were included, along with an equal cohort of anatomy-matched patent controls. Patient-specific pulsatile rigid-wall simulations were performed using SimVascular with individualized geometries and boundary conditions. Abnormal time-averaged wall shear stress (TAWSS) was defined as <10 or >70 dynes/cm2.

RESULTS: Nine patients (36 target vessels) experienced 10 branch occlusions. Postoperative pressure and flow did not differ significantly between occluded and patent renal or mesenteric branches. However, occluded renal and mesenteric branches demonstrated significantly larger postoperative areas of abnormal TAWSS compared with controls (renal: 14.5% versus 5.9%, P=0.003; mesenteric: 17.7% versus 9.9%, P=0.035). Logistic generalized estimating equation modeling showed abnormal TAWSS to be a significant predictor of renal branch occlusion (P=0.0085). Model estimates suggested occlusion probabilities of 1.1%, 31%, and 94% at 0%, 10%, and 20% abnormal TAWSS surface area, respectively. A cluster-bootstrapped receiver operating characteristic curve (area under the curve, 0.876) identified a >10.2% threshold that correctly classified 92% of renal occlusions. Abnormal TAWSS frequently localized to distal stent-artery interfaces.

CONCLUSIONS: Elevated abnormal TAWSS within stented renal branches is associated with subsequent branch occlusion after fenestrated and branched endovascular aneurysm repair. Computational flow simulation-derived TAWSS thresholds may help identify high-risk branches before failure, warranting prospective validation.