Control Strategies for Afterload Reduction With an Artificial Vasculature Device

Abstract

Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) is being developed that may better facilitate myocardial recovery than VAD by controlling the afterload experienced by the native heart and controlling the pulsatile energy entering into the arterial system from the device, potentially reconditioning the arterial system properties. The AVD is a valveless, 80 ml blood chamber with a servo-controlled pusher plate connected to the ascending aorta by a vascular graft. Control algorithms for the AVD were developed to maintain any user-defined systemic input impedance (IM) including resistance, elastance, and inertial components. Computer simulation and mock circulation models of the cardiovascular system were used to test the efficacy of two control strategies for the AVD: 1) average impedance position control (AIPC)-to maintain an average value of resistance during left ventricular (LV) systole and 2) instantaneous impedance force feedback (IIFF) and position control (IIPC)-to maintain a desired value or profile of resistance and compliance. Computer simulations and mock loop tests were performed to predict resulting cardiovascular pressures, volumes, flows, and the resistance and compliance experienced by the native LV during ejection for simulated normal, failing, and recovering LV. These results indicate that the LV volume and pressure decreased, and the LV stroke volume increased with decreasing IM, resulting in an increased ejection fraction. Although the AIPC algorithm is more stable and can tolerate higher levels of sensor errors and noise, the IIFF and IIPC control algorithms are better suited to maintain any instantaneous IM or an IM profile. The developed AVD impedance control algorithms may be implemented with current VADs to promote myocardial recovery and facilitate weaning.

Object‐Oriented Lumped‐Parameter Modeling of the Cardiovascular System for Physiological and Pathophysiological Conditions

“…These consist of a pulsatile pump, tubes, and compliance chambers, and are commonly used in cardiovascular research due to their versatility and low cost. [ 28–33 ] Nevertheless, these systems are limited to simplified representations of the cardiovascular network and building an in vitro model of the entire vascular tree remains challenging. [ 34 ]…”

Mock circulatory loop applications for testing cardiovascular assist devices and in vitro studies

“…However, when more circulations are concerned, or when the operation of some medical devices affects different circulations, more circulatory loops are required to be coupled to the MCL. Since coronary artery disease accounts for a large proportion of cardiovascular disease, many scholars have incorporated coronary circulation in the MCL ( Geven et al, 2004 ; Koenig et al, 2004 ; Pantalos et al, 2004 ; Park et al, 2006 ; Kaebnick et al, 2007 ; Park et al, 2007 ; Zannoli et al, 2009 ; Schampaert et al, 2011 ; Giridharan et al, 2012 ; Schampaert et al, 2014 ; Madukauwa-David et al, 2020 ). The flow characteristics of coronary circulation can be realized by means of the stepping motor cooperating with the valve ( Calderan et al, 2016 ), the parallel pipeline with the solenoid valve ( Rezaienia et al, 2017 ), PID control ( Gregory et al, 2020 ), the piston pump ( Madukauwa-David et al, 2020 ), etc.…”

In Vitro Evaluation of Control Strategies for an Artificial Vasculature Device

“…Since the AVD was programmed to produce an impedance less than or equal to that of the normal vasculature, the valve remains closed during cardiac systole. Under such conditions, the relationship between the pump volume, V, rate of change of pump volume, V', pump pressure, P, resistance, R, and compliance, C, is given by [12] :…”

“…The relationship between the pump volume, V, rate of change of pump volume, V', pump pressure, P, Resistance, R and compliance, C, is given by [12] R P CP'…”

“…Our computer simulation studies [11][12], an initial step in the device design process, demonstrated that the AVD has the potential to produce greater diastolic coronary perfusion, reduce ventricular workload while continuing to enable the left ventricle to fill and eject at normal volumes, and allow the heart to eject against a lower afterload (resistance and elastance) compared to continuous and asynchronous pulsatile assist techniques. It is our working hypothesis that afterload reduction during myocardial ejection using the AVD approach will augment the myocardial recovery process.…”