Comparison of hemodynamics in the ascending aorta between pulsatile and continuous flow left ventricular assist devices using computational fluid dynamics based on computed tomography images

This study aims to investigate differences in hemodynamic conditions in the thoracic aorta for pulsatile and continuous-flow left ventricular assist devices (LVADs) using computational fluid dynamics (CFD). Patient-specific models were reconstructed from three patients with continuous-flow LVAD (HeartMate II, Thoratec Corporation) and three patients with biventricular assist devices (Excor, Berlin Heart) where only the aortic part was included in the simulations. CFD simulations were performed with constant inflow for the continuous-flow LVADs and time-varying inflow for the pulsatile devices. Differences in flow patterns, wall shear stress (WSS), and dynamic pressure in the ascending aorta were compared for both cases. Retrograde flow patterns were observed in all cases proximal to the location of the outflow cannula anastomosis site. On average, dynamic pressures derived from the retrograde flow velocities were higher in the continuous-flow group with large variations dependent on the angle of the cannula anastomosis relative to the ascending aorta (continuous group: 0.14±0.2mmHg, pulsatile group: 0.013±0.008mmHg). Elevated WSS contralaterally to the anastomosis site was observed in three of the six models with higher values for the continuous cases. Lower WSS and reduced pressure in the ascending aorta, both favorable hemodynamic conditions, were found in pulsatile versus continuous-flow LVADs by means of CFD. These findings indicate, along with clinical observations reported by others, the superior performance of pulsatile LVADs.