Pressure, Flow Rate and Operating Speed Characteristics of a Continuous Flow Left Ventricular Assist Device During Varying Speed Support

Selim Bozkurt

doi:10.1109/access.2020.3009264

Abstract

Hydraulic performance of Continuous Flow Left Ventricular Assist Devices depends on their pressure head and flow rate relations. Hydraulic characteristics of these devices are expressed by pressure head and flow rate loops in a pulsatile environment as they are implanted between left ventricular apex and aorta. Nonetheless, constant speed Continuous Flow Left Ventricular Assist Device support causes complications due to altered blood flow in the patients’ body. Therefore, beat-to-beat varying speed Continuous Flow Left Ventricular Assist Device support algorithms have been proposed to operate these devices in synchronized co-pulsating or counter-pulsating modes which can generate more physiological blood flow in the circulatory system. However, the effect of speed variation on the pressure head and flow rate loops remains unclear during varying speed Continuous Flow Left Ventricular Assist Device support. In this study, pressure head, flow rate and operating speed relations during co-pulsating and counter-pulsating pump support in a Continuous Flow Left Ventricular Assist Device were analyzed utilizing numerical simulations. Simulation results show that pressure head - flow rate - operating speed loops can express Continuous Flow Left Ventricular Assist Device characteristics better during varying speed heart pump support. Moreover, pump flow rate - operating speed and pressure head - operating speed diagrams show the dynamic behavior of a heart pump, including also the speed. Therefore, understanding the relationship between speed, flow rate and the pressure difference across a pump may help to develop novel beat-to-beat operating modes to improve Continuous Flow Left Ventricular Assist Device support.

Highlights

Continuous Flow Left Ventricular Assist Devices (CF-LVADs) are used to bridge the time between the decision to transplant and the actual transplantation in end-stage heart failure patients
Point 1 shows the closure of mitral valve and onset of the systolic phase, which are noticeable in the CF-LVAD H-Q loops for all the support modes
Point 2 in the CF-LVAD H-Q loop shows the opening of aortic valve

Summary

Introduction

Continuous Flow Left Ventricular Assist Devices (CF-LVADs) are used to bridge the time between the decision to transplant and the actual transplantation in end-stage heart failure patients. CF-LVAD hydraulic performance for steady flow depends on the pump pressure head and flow rate (H-Q) characteristics at a certain speed [1]. CF-LVAD H-Q characteristics can be used to estimate the pump flow rate and left ventricular pressure under constant speed pump support [2]. CF-LVADs operate in a pulsatile environment because they are implanted between the apex of the left ventricle and ascending aorta, [3]. The associate editor coordinating the review of this manuscript and approving it for publication was Chaitanya U.

Methods

Results

Discussion

Conclusion