Left Ventricular Hemodynamics with an Implanted Assist Device: An In Vitro Fluid Dynamics Study

Left ventricle assist devices (VADs) aid the heart pumping blood into the systemic circulation and grant the required cardiac output (CO) when the heart itself cannot provide it. However, it is unclear how effective these devices are at restoring not only physiological CO values but also normal intraventricular hemodynamics. In this work, the modified hemodynamics due to a VAD implantation is studied in vitro using an elastic ventricle made of silicone, which is incorporated into a pulse-duplicator setup prescribing a realistic pulsatile flow. Thereafter, a continuous axial pump is connected at the ventricle apex to mimic a VAD and its effect on the ventricular hemodynamics is investigated as a function of the pump flow suction. Using particle image velocimetry (PIV), we observe that the continuous pump flow effectively provides unloading on the ventricle and yields an increased CO. Conversely, the continuous blood suction from the ventricle apex deeply alters the hemodynamics and, in addition, the VAD obstruction in the ventricle behaves as a bluff body that affects the vorticity distribution in the LV thus creating a stagnant region at the ventricle apex. This phenomenon is rationalized by measuring in a modified set-up the benefits on the hemodynamics of a flush-mounted device. Additionally, the suction operated by the VAD reduces the ventricular pressure and yields an increase in the swirling motion around the ventricle axis, in a similar fashion as the bath-tub vortex effect, thus further modifying the intraventricular hemodynamics with respect to healthy conditions.