Effect of Left Ventricular Assist Device Outflow Conduit Anastomosis Location on Flow Patterns in the Native Aorta

Abstract

Computational fluid dynamics (CFD) models were developed to investigate the altered fluid dynamics of the native aorta in patients with a left ventricular assist device (LVAD). The objective of this study was to simulate the effect of LVAD aortic outflow conduit location on the 3-D flow in the native aorta over a range of boundary conditions. The fluid mechanics of three different surgical geometries [(P), proximal, (D), distal and (IP), in-plane] were studied and the implications for short- and long-term medical consequences explored by evaluating the flow fields, wall shear, and hemolysis. The greatest disruptions in the normal aortic flow pattern occurred with series flow conditions, when flow through the aortic valve was minimal. Under series conditions, circulation in the proximal aorta is retrograde, originating from the LVAD outflow conduit. The (P) geometry provided the most blood washout of the proximal aorta, with a larger region of slow-moving flow observed in the (D) and (IP) models. Wall shear stress was reduced for the (IP) geometry, which lacks the direct flow impingement present in the (P) and (D) models. Clinically, the (D) and (IP) geometries require less traumatic surgeries and probably are better tolerated by the patient. In this situation, the (IP) geometry suggests improvement in both increased flow to the proximal aorta and decreased shear stress compared with (D). However, the (D) and (IP) configurations are not recommended for patients with low or no flow from the heart because of the lack of blood washout near the aortic valve and therefore possible thrombus formation in that area.