Changing pulsatility by delaying the rotational speed phasing of a rotary left ventricular assist device

Abstract

Continuous-flow left ventricular assist devices (LVADs) have improved the prognosis of end-stage heart failure. However, continuous-flow LVADs diminish pulsatility, which possibly result in bleeding, aortic insufficiency, and other adverse effects. We previously developed a novel control system for a continuous-flow LVAD (EVAHEART; Sun Medical), and demonstrated that we could create sufficient pulsatility by increasing its rotational speed (RS) in the systolic phase (Pulsatile Mode) in the normal heart model. Here, we aimed to evaluate differences between systolic assist with advanced and delayed loads by shifting the timing of increased RS. We implanted EVAHEART in six goats (55.3 ± 4.3 kg) with normal hearts. We reduced their heart rates to <60 bpm using propranolol and controlled the heart rates at 80 and 120 bpm using ventricular pacing. We shifted the timing of increasing RS from -60 to +60 ms in the systolic phase. We found significant increases in all the following parameters when assessments of delayed timing (+60 ms) were compared with assessments of advanced timing (-60 ms): pulse pressure, mean dP/dt max of aortic pressure, and energy-equivalent pulse pressure. During continuous-flow LVAD support, pulsatility can be controlled using a rotary pump. In particular, pulsatility can be shifted by delaying increased RS.

In vitro performance of trans‐valve left ventricular assist device installed at aortic valve position

“…Travis et al 22 reported that PF LVAD patients at a low support level restored SHE values within 2.5% of baseline normal values, whereas CF LVAD patients at low support had diminished SHE values by more than 93% of baseline normal values, and this effect was even more pronounced at a higher support level. 22 Date et al 6 investigated pulsatility using EEP under CF LVAD support with pump speed modulation, and the SHE value increased by 244% from the CF mode in an animal experiment. 6 When the trans-valve LVAD does not apply hydrodynamic pulsatile energy into blood flow, the SHE value is lower than that of PF LVAD and CF LVAD with the speed modulation.…”

“…22 Date et al 6 investigated pulsatility using EEP under CF LVAD support with pump speed modulation, and the SHE value increased by 244% from the CF mode in an animal experiment. 6 When the trans-valve LVAD does not apply hydrodynamic pulsatile energy into blood flow, the SHE value is lower than that of PF LVAD and CF LVAD with the speed modulation. However, the trans-valve LVAD has an advantage in that it can preserve pulsatility without any complicated mechanism.…”

“…At present, the pump speed modulation of the CF blood pump is being studied to improve pulsatility of blood flow 5‐7 . Furthermore, new pulsatile left ventricular assist devices (LVADs) are being developed to support cardiac function with pulsatile flow (PF) 8,9 …”

Development of rear‐impeller axial flow blood pump for realization of axial flow blood pump installed at aortic valve position

“…The new concept of the axial VAD in 1989 has several merits. An axial VAD serially connected with the natural heart, such as the valvo pump, can support blood circulation with pulsatile flow generated by the natural heart without pump speed modulation . However, realization of the valvo pump concept has not occurred because it is difficult to develop a miniature high‐power motor to meet the requirement of the valvo pump under current motor technology.…”

“…An axial VAD serially connected with the natural heart, such as the valvo pump, can support blood circulation with pulsatile flow generated by the natural heart without pump speed modulation. 15,16 However, realization of the valvo pump concept has not occurred because it is difficult to develop a miniature high-power motor to meet the requirement of the valvo pump under current motor technology. Thus, a new concept of the valvo pump was proposed: The trans-valve axial VAD, in which the motor is installed in the left ventricle, and the impeller is placed at the aortic valve position.…”