CARD4: In Silico Investigation Of The Effect Of Outflow Graft Narrowing On The Hemodynamics In LVAD Patients

Abstract

Background: Outflow graft (OG) stenosis is a major complication of LVAD therapy. It causes an increase in the resistance along the OG, leading to pump malfunction and potentially poor clinical outcomes. This study aims at fully characterizing the effect of different degrees of OG stenosis on the hemodynamics. Methods: Computational Fluid Dynamics (CFD) simulations were performed in a patient-derived aortic arch anatomy, with 10- and 14-mm diameter LVAD OG virtually implanted at the aortic root. A stenosis was created just proximal to the anastomosis, with increasing degrees of severity. Simulations performed without stenosis, were considered as reference. Resistance/Capacitance elements were used as outlet boundary conditions. Constant inflow (5 L/min) was applied at the proximal end of the OG. Results: The smallest (25% area reduction) stenosis showed minor changes in pressure gradient and shear stresses for both OG diameters. For a large (~50% area reduction) stenosis, the large size OG showed minor hemodynamic changes, whereas the 10-mm OG resulted in a significant pressure gradient and increased shear stress. All cases with larger than 50% lumen reduction stenosis presented a significant increase in all metrics. The OG stenosis creates a strong jet that enters the aorta and impinges on the contralateral artery wall. This jet results in recirculation areas on the aortic root, specifically adjacent to the closed aortic valve. Conclusion: The effect of stenosis tends to be less severe for the larger size OG. Even though the increase in resistance induced by the stenosis could seem insignificant, the stenosis significantly modifies the hemodynamics. Further study is needed to assess the potential thrombogenicity of OG stenosis and determine the threshold for intervention.