Computational fluid dynamics of a novel perfusion strategy using direct perfusion of a left carotid-subclavian bypass during hybrid thoracic aortic repair

Objective: We aimed to computationally evaluate the effects of direct cerebral perfusion strategy through a left carotid-subclavian bypass on hemodynamics in a patient-specific thoracic aorta model. Methods: Between July 2016 and March 2019, eleven consecutive patients underwent single-stage frozen elephant trunk operation using the left carotid-subclavian bypass with a side graft anastomosis and a right axillary cannulation for systemic and brain perfusion. A multiscale model realized coupling 3D computational fluid dynamics was developed and validated with in vivo data. A model comparison with direct antegrade cannulation of all epiaortic vessels was performed. Wall shear stress, wall shear stress spatial gradient, and localized normalized helicity were selected as hemodynamic indicators. Four cerebral perfusion flows were tested (6 to 15 ml/kg/min). Results: Direct cerebral perfusion of the left-subclavian bypass resulted in higher flow rates with augmented speeds in all epiaortic vessels in comparison with traditional perfusion model. At the level of left vertebral artery, a speed of 22.5 vs 21 ml/min and mean velocity of 3.07 cm/s vs 2.93 cm/s were registered, respectively. With a cerebral perfusion flow of 15 ml/kg, lower left vertebral artery wall shear stress (1.596 vs 2.030 N/m2) and wall shear stress gradient (1445 vs 5882 N/m3) were observed. A less disturbed flow considering the localized normalized helicity was documented. Similar results persisted at different cerebral perfusion flows. No patients experienced neurological/spinal cord damages. Conclusions: The direct perfusion of a left-carotid bypass proved to be cerebroprotective, resulting in a more physiological and stable anterior and posterior cerebral perfusion.