Abstract
Continuous-flow left ventricular assist devices (CF-LVADs) generally operate at a constant speed, which reduces pulsatility in the arteries and may lead to complications such as functional changes in the vascular system, gastrointestinal bleeding, or both. The purpose of this study is to increase the arterial pulse pressure and pulsatility by controlling the CF-LVAD flow rate. A MicroMed DeBakey pump was used as the CF-LVAD. A model simulating the flow rate through the aortic valve was used as a reference model to drive the pump. A mock circulation containing two synchronized servomotor-operated piston pumps acting as left and right ventricles was used as a circulatory system. Proportional-integral control was used as the control method. First, the CF-LVAD was operated at a constant speed. With pulsatile-speed CF-LVAD assistance, the pump was driven such that the same mean pump output was generated. Continuous and pulsatile-speed CF-LVAD assistance provided the same mean arterial pressure and flow rate, while the index of pulsatility increased significantly for both arterial pressure and pump flow rate signals under pulsatile speed pump support. This study shows the possibility of improving the pulsatility of CF-LVAD support by regulating pump speed over a cardiac cycle without reducing the overall level of support.
Highlights
Continuous-flow left ventricular assist devices (CFLVADs) generally operate at a constant speed
Comparative studies showed that loss of von Willebrand factor is higher under CFLVAD support than under pulsatile assist device support [12, 13], which may be interpreted as pulsatile circulatory support being more beneficial for Continuous-flow left ventricular assist device (CF-LVAD) patients
The aortic pressure and pump flow rate under pulsatile- and constant-speed CF-LVAD assistance modes are given in Fig. 4a, b, respectively
Summary
Continuous-flow left ventricular assist devices (CFLVADs) generally operate at a constant speed. Patients under pulsatile support exhibit less remodeling and functional changes in their vascular system compared to those of patients under constant-flow support [2,3,4,5,6,7,8,9]. This leads to less gastrointestinal (GI) bleeding, aortic wall remodeling, and better vascular auto-regulatory function. Comparative studies showed that loss of von Willebrand factor is higher under CFLVAD support than under pulsatile assist device support [12, 13], which may be interpreted as pulsatile circulatory support being more beneficial for CF-LVAD patients. Inflammatory responses reportedly occur at a lower rate in patients under pulsatile support as well [18, 19]
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