Biomechanical implications of the fenestration structure after thoracic endovascular aortic repair.

The inadequate landing zone during thoracic endovascular aortic repair (TEVAR) could be resolved by fenestration technology. The fenestration structure consists of a main endograft and a left subclavian artery (LSA) stent-graft. The purpose of this study is to assess the biomechanical implications of the protruding segment (PS) of the LSA stent-graft after TEVAR with in situ fenestration (ISF-TEVAR). The PS is characterized by the protruding length and centerline angle between the LSA and PS. An idealized three-dimensional geometric model of the human aorta was constructed as the reference benchmark. We designed nine postoperative aortic geometries with different protruding lengths (5, 10, 15 mm) and centerline angles (-20°, 0°, +20°). The blood was assumed to be non-Newtonian and the three-element Windkessel model was applied to reproduce physiological pressure waveforms. The interaction between the blood and vessel wall was captured by a two-way fluid-structure method. We also considered the impact of the fenestration structure on the vessel wall. Long protruding length (15 mm) and the retrograde angle (+20°) result in a markedly reduced LSA flow ratio (1.3%). There is a pressure difference between the inner and outer walls of the PS. The region around the PS is more prone to thrombosis. The flow stability and turbulence intensity of downstream blood of the PS gradually deteriorate. The largest deformed region moves from the aortic arch to the ascending aorta after ISF-TEVAR. The postoperative hemodynamics largely depends on the protruding length and angle of the LSA stent-graft. The configurations should be carefully controlled during ISF-TEVAR.