Near-wall hemodynamic changes in subclavian artery perfusion induced by retrograde inner branched thoracic endograft implantation

Abstract

Objective: Left subclavian artery (LSA)-branched endografts with retrograde inner branch configuration (thoracic branch endoprosthesis [TBE]) offer a complete endovascular solution when LSA preservation is required during zone 2 thoracic endovascular aortic repair. However, the hemodynamic consequences of the TBE have not been well-investigated. We compared near-wall hemodynamic parameters before and after the TBE implantation using computational fluid dynamic simulations. Methods: Eleven patients who had undergone TBE implantation were included. Three-dimensional aortic arch geometries were constructed from the pre- and post-TBE implantation computed tomography images. The resulting 22 three-dimensional aortic arch geometries were then discretized into finite element meshes for computational fluid dynamic simulations. Inflow boundary conditions were prescribed using normal physiological pulsatile circulation. Outlet boundary conditions consisted of Windkessel models with previously published values. Blood flow, modeled as Newtonian fluid, simulations were performed with rigid wall assumptions using SimVascular's incompressible Navier-Stokes solver. We compared well-established hemodynamic descriptors: pressure, flow rate, time-averaged wall shear stress (TAWSS), the oscillatory shear index (OSI), and percent area with an OSI of >0.2. Data were presented on the stented portion of the LSA. Results: TBE implantation was associated with a small decrease in peak LSA pressure (153 mm Hg; interquartile range [IQR], 151-154 mm Hg vs 159 mm Hg; IQR, 158-160 mm Hg; P = .005). No difference was observed in peak LSA flow rates before and after implantation: 40.4 cm3/ (IQR, 39.5-41.6 cm3/s) vs 41.3 cm3/s (IQR, 37.2-44.8 cm3/s; P = .59). There was a significant postimplantation increase in TAWSS (15.2 dynes/cm2 [IQR, 12.2-17.7 dynes/cm2] vs 6.2 dynes/cm2 [IQR, 5.7-10.3 dynes/cm2]; P = .003), leading to decreases in both the OSI (0.088 [IQR, 0.063 to –0.099] vs 0.1 [IQR, 0.096-0.16]; P = .03) and percentage of area with an OSI of >0.2 (10.4 [IQR, 5.8-15.8] vs 15.7 [IQR, 10.7-31.9]; P = .13). Neither LSA side branch angulation (median, 81°, IQR, 77°-109°) nor moderate compression (16%-58%) seemed to have an impact on the pressure, flow rate, TAWSS, or percentage of area with an OSI of >0.2 in the stented LSA. Conclusions: The implantation of TBE produces modest hemodynamic disturbances that are unlikely to result in clinically relevant changes. : Clinical Relevance: The Gore thoracic branch endoprosthesis represents the only commercially available stent graft in the United States for the treatment of aortic arch pathologies involving the left subclavian artery. The implantation of endografts cause alterations in flow patterns that, in turn, can have a significant impact on long-term device durability and the prognosis of the patient. The results of this computational modelling study provide important data regarding the hemodynamic performance of the thoracic branch endoprosthesis relevant to the associated clinical outcomes and subsequent implications on device durability.

Keywords

• Branched endografts
• Computational fluid dynamics
• Left subclavian artery revascularization
• Wall shear stress