Control of ventricular unloading using an electrocardiogram‐synchronized pulsatile ventricular assist device under high stroke ratios

Abstract

Pulsatile ventricular assist devices (pVADs) yield a blood flow that imitates the pulsatile flow of the heart and, therefore, could diminish the adverse events related to the continuous flow provided by the ventricular assist devices that are commonly used. However, their intrinsic characteristics of larger size and higher weight set a burden to their implantation, that along with the frequent mechanical failures and thrombosis events, reduce the usage of pVADs in the clinical environment. In this study, we investigated the possibility to reduce the pump size by using high pump stroke ratios while maintaining the ability to control the hemodynamics of the cardiovascular system (CVS). In vitro and in vivo experiments were conducted with a custom pVAD implemented on a hybrid mock circulation system and in five sheep, respectively. The actuation of the pVAD was synchronized with the heartbeat. Variations of the pump stroke ratio, time delay between the pump stroke and the heart stroke, as well as duration of the pump systole in respect to the total cardiac cycle duration were used to evaluate the effects of various pump settings on the hemodynamics of the CVS. The results suggest that by varying the operating settings of the pVAD, a pulsatile flow that provides physiological hemodynamic parameters, as well as a control over the hemodynamic parameters, can be achieved. Additionally, by employing high pump stroke ratios, the size of the pVAD can be significantly reduced; however, at those high pump stroke ratios, the effect of the other pump parameters diminishes.

Innovative experimental animal models for real‐time comparison of antithrombogenicity between two oxygenators using dual extracorporeal circulation circuits and indocyanine green fluorescence imaging

“…Since no thromboembolism was observed in the autopsy findings, we assumed that the thrombi formed in the oxygenator were not flushed out of the oxygenator by the pulsatile flow but were inhibited at the very early stage of the thrombus‐formation cascade. Various studies on pulsatile flow in ECMO and ventricular assist devices have been reported not only in basic research but also in clinical applications 31–33 . However, although improvement of gas exchange capacity of oxygenators with the pulsatile flow has been reported, 34–36 we could not find any reports on the inhibitory effect of pulsatile flow on thrombus formation.…”

A Soft Robotic Actuator System for In Vivo Modeling of Normal Pressure Hydrocephalus

“…Commercialized pump systems and valves were considered, but no system was found that allows for sufficiently fast switching of the flow direction and the generation of sufficiently high pressure for the actuation of the utilized soft robotic end actuators and balloon catheters. In order to meet the above requirements, we developed a dedicated in vivo actuation device that is based on a linear voice coil motor (LVCM) [26], [27]. A schematic of the custom actuation device and its control structure for the later in vivo application is shown in Figure 3.…”

Physiologic Data-Driven Iterative Learning Control for Left Ventricular Assist Devices

“…Nonetheless, recent studies have reported strong evidence that the lack of pulsatility can negatively affect the endothelial and peripheral vascular function (25-27) and, hence, increase the risk of non-surgical bleeding (28). Additionally, various studies highlight the better control of ventricular unloading and patient's hemodynamics when VADs that effectively resemble the pulsatile flow conditions are deployed (29)(30)(31)(32).…”