Computational fluid dynamics of a novel perfusion strategy during hybrid thoracic aortic repair

Background and aim: To mitigate the risk of perioperative neurological complications during frozen elephant trunk procedures, 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, 11 consecutive patients underwent frozen elephant trunk operation using the left carotid-subclavian bypass with a side graft anastomosis and right-axillary cannulation for systemic and brain perfusion. A multiscale model realized coupling three-dimensional computational fluid dynamics was developed and validated with in vivo data. 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 the left vertebral artery (LVA), a speed of 22.5 vs 21 mL/min and mean velocity of 3.07 vs 2.93 cm/s were registered, respectively. With a cerebral perfusion flow of 15 mL/kg, lower LVA 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. No patients experienced neurological/spinal cord damages.

Conclusions: Direct perfusion of a left carotid bypass proved to be cerebroprotective, resulting in a more physiological and stable anterior and posterior cerebral perfusion.