Helical Flow Component of Left Ventricular Assist Devices (LVADs) Outflow Improves Aortic Hemodynamic States.

BACKGROUND Although LVADs are confirmed to have strong effects on aortic hemodynamics, the precise mechanisms of the helical flow component of LVAD outflow are still unclear. MATERIAL AND METHODS To clarify these effects, 3 cases - normal case, flat flow case, and realistic flow case - were designed and studied by using the CFD approach. The normal case denoted the normal aorta without LVAD support, and the flat flow case represented the aorta with the outflow cannula. Similarly, the realistic flow case included the aortic model, the model of outflow cannula, and the model of LVAD. The velocity vector, blood streamline, distribution of wall shear stress (WSS), and the local normalized helicity (LNH) were calculated. RESULTS The results showed that the helical component of LVAD outflow significantly improved the aortic hemodynamics. Compared with the flat flow case, the helical flow eliminated the vortex near the outer wall of the aorta and improved the blood flow transport (normal case 0.1 m/s vs. flat flow case 0.14 m/s vs. realistic flow case 0.30 m/s) at the descending aorta. Moreover, the helical flow was confirmed to even the distribution of WSS, reduce the peak value of WSS (normal case 0.92 Pa vs. flat flow case 7.39 Pa vs. realistic flow case 5.2Pa), and maintain a more orderly WSS direction. CONCLUSIONS The helical flow component of LVAD outflow has significant advantages for improving aortic hemodynamic stability. Our study provides novel insights into LVAD optimization.