Increasing the Transmitted Flow Pulse in a Rotary Left Ventricular Assist Device

Abstract

Long-term rotary left ventricular assist devices (LVADs) are increasingly employed to bridge patients with end-stage heart failure to transplant or as a destination therapy. Significant recent device development has increased patient support times, shifting further development focus toward physiologically sensitive control of the pump operation. Sensorless control of these devices would benefit from increased observability of the ventricular volume/preload to the pump, in order to regulate flow based on preload, imitating the native Frank-Starling flow control. Monitoring the transmitted flow pulse through the pump has been used as a surrogate for preload, although means of maximizing its transmission are not clear. However, it is known that a flat hydraulic performance curve of the rotary pump induces high changes in flow for a given change in pressure head. The aim of this study was to determine geometric pump parameters responsible for increasing this flow pulse transmission and to demonstrate this increase in vitro. The sensitivity of the performance gradient to blade angles, blade heights, blade clearance, and channel areas were studied. Resulting pressure head, flow, and hydraulic efficiency were analyzed with respect to textbook designed procedures. Then pumps with comparably "flat" and "steep" performance curves were used to simulate LVAD support in vitro over a range of pump flow rates to observe the transmitted flow pulsatility. It was found that an outlet blade angle of 90°, inlet blade angle between 25 and 45°, and large throat area generated a "flatter" performance curve. The transmitted flow pulsatility through a pump with a flat performance curve was 68% higher than that of a steep performance curve at a flow rate of 5 L/min. Substantial gains in the observability of LVAD preload/resident blood volume in the ventricle exist through the careful selection of specific pump geometries.

Relative contributions from the ventricle and arterial tree to arterial pressure and its amplification: an experimental study

“…1 ). Fluid entered the ventricle from the left atrium via a low vibration swing mitral valve [as used previously ( 7 , 9 )] and exited through a trileaflet-molded silicone aortic valve (LifeGroup, Eindhoven, The Netherlands). The working fluid was water.…”

Synchronized Pulsatile Speed Control of Turbodynamic Left Ventricular Assist Devices: Review and Prospects

“…Despite this constant speed, the flow through a turbodynamic VAD (tVAD) is slightly pulsatile due to the remaining cardiac function. The pulsatility of the flow depends on the pressure head (difference between the downstream and upstream pressures of the pump) and on the pump characteristics . However, this flow pulsatility is smaller than the pulsatility in physiological pulsatile flow .…”

Pulmonary Valve Opening With Two Rotary Left Ventricular Assist Devices for Biventricular Support

“…In addition, for the particular purpose of PVO, a steep H‐Q gradient is recommended. Meanwhile, in instances where greater flow sensitivity and pulsatility at constant speed is desired, a flat H‐Q gradient is suggested .…”