Effects of two different surgical methods for endovascular repair of the thoracic aorta on the hemodynamics of the left subclavian artery

Abstract

Background: Some clinicians use endograft to partially cover the left subclavian artery (LSA) ostium or multilayer flow modulator (MFM) to mitigate cases with an insufficient landing area in thoracic endovascular aortic repair(TEVAR) treatment. So we used computational fluid dynamics (CFD) to study the effects of two surgical methods on the hemodynamics of the LSA, due to they may affect the long-term patency rate of the LSA. Methods: The digital model of the aortic arch was established and named model A, which only included supraarch branch the LSA. The simulated digital model of the MFM was implanted into model A, named as model B. By directly covering one half of the LSA ostium, which was named as model C. All established models were imported into the Gambit grid division software for grid division and were subsequently imported into the Fluent software for hemodynamic numerical simulation and calculation. The changes in the related hemodynamic parameters of the LSA after implantation of the two stents were analyzed and compared. Results: Under the same aortic inlet flow, in model C, the lumen flow of the LSA was obviously reduced and the distal descending aorta flow was increased, the local blood flow velocity of LSA ostium increased and whole blood flow velocity at the distal end decreased. The average wall shear stress(WSS) of the LSA was significantly decreased. Meanwhile there was an obvious turbulent flow in the LSA lumen, and the related blood flow state was disordered. However, all changes in model B was occured, they changed slightly compared with model A. Conclusion: CFD research confirmed that the implantation of an MFM had little influence on the hemodynamics of the LSA. In contrast, the implantation of an endograft partially covering the LSA ostium increased the local ostium velocity. But it reduced the global flow rate, velocity, and average wall shear stress at the distal end. This change is likely to cause a long-term hardening and an acute thrombosis of the LSA artery. Nevertheless, this operation can also be used in specific clinical cases.