Preoperative Computational Fluid Dynamics Simulation of the Best Anastomosis Site and Angle of the Outflow Graft and Ascending Aorta in Continuous Flow Mechanical Assist Devices

Abstract

Purpose Left ventricle assist devices (LVAD) have contributed to improve survival and quality of life in patients with advanced heart failure, in temporary or lifetime support. Despite technological, bio-compatibility and hemodynamic progress, patients with LVAD have still a relevant incidence of adverse events, such as disabling stroke. The outflow cannula (OC) position and angulation, and the anastomosis site seem to modify the flow in the ascending aorta (AA), and consequently the incidence of cerebral embolism and aortic cusps stress. Methods We evaluated the combination of LVAD flow and the residual cardiac output pulsatile flow with computational fluid dynamics (CFD) software based on CT Scan images. Results Two patients with centrifugal pump LVAD underwent CT Scan regardless of this study, respectively at 7 months and 1.5 years after LVAD implant. We analyzed CT images and made a CFD reconstruction of the anastomosis site, to evaluate the flow in AA. At the same time, in a bench validation test we anastomosed a dacron 32 mm graft (reproducing the AA) and a 14 mm graft (reproducing the OC). We simulated the difference in flow and turbulence, according to different angles of the anastomosis, and the alternative distances from the major cranial branches. Following results of the CFD analysis, we can affirm that it is possible to simulate the optimal flow, improving the laminar flow and reducing the turbulence in the aortic lumen. Moreover, based on the desired angle of the aortic-graft anastomosis, the surgeon can perform the anastomosis with the best shape of the OC (cutting the graft with the angle obtained by the CFD simulation, and incising the AA with the right extension). Conclusion The optimized combination of flows could reduce the incidence of thromboembolic events, aortic endothelium stress, and aortic cusps stress/thrombosis. Further studies are necessary to validate this technology in clinical and surgical practice.