A Mathematical Model to Evaluate Control Strategies for Mechanical Circulatory Support

Abstract

Continuous flow ventricular assist devices (VADs) for mechanical circulatory support (MCS) are generally smaller and believed to be more reliable than pulsatile VADs. However, regarding continuous flow, there are concerns about the decreased pulsatility and ventricular unloading. Moreover, pulsatile VADs offer a wider range in control strategies. For this reason, we used a computer model to evaluate whether pulsatile operation of a continuous flow VAD would be more beneficial than the standard constant pump speed. The computer model describes the left and right ventricle with one-fiber heart contraction models, and the systemic, pulmonary, and coronary circulation with lumped parameter hemodynamical models, while the heart rate is regulated with a baroreflex model. With this computer model, both normal and heart failure hemodynamics were simulated. A HeartMate II left ventricular assist device model was connected to this model, and both constant speed and pulsatile support were simulated. Pulsatile support did not solve the decreased pulsatility issue, but it did improve perfusion (cardiac index and coronary flow) and unloading (stroke work and heart rate) compared with constant speed. Also, pulsatile support would be beneficial for developing control strategies, as it offers more options to adjust assist device settings to the patient's needs. Because the mathematical model used in this study can simulate different assist device settings, it can play a valuable role in developing mechanical circulatory support control strategies.

Flow Modulation Algorithms for Continuous Flow Left Ventricular Assist Devices to Increase Vascular Pulsatility: A Computer Simulation Study

“…Modulation of blood pump motor speeds/flow has been suggested as a potential mechanism to artificially increase vascular pulsatility in both ventricular assist devices 2,5,19,24,26,33,34 and total artificial heart. 10,16,17,27 Flow modulation of ventricular assist devices are affected by the timing of flow modulation to the native myocardial contraction.…”

Numerical Optimal Control of Turbo Dynamic Ventricular Assist Devices

“…A square-wave speed profile was applied by Bearnson et al [11] and Bourque et al [12] to increase arterial pulse pressure, where the speed profile was not synchronized to the cardiac cycle. Different types of speed profiles, synchronized to the natural cardiac cycle, have been applied in silico and in vitro to analyze their influence on perfusion, pulse pressure and ventricular unloading [13][14][15][16][17][18]. In vivo experiments have been conducted to validate this approach [19,20].…”

On the effect of aortic root geometry on the coronary entry-flow after a bileaflet mechanical heart valve implant: a numerical study

“…One should consider the inertia of the fluid of all the neglected parts of the network, combined with the fact that the coronary arteries have a considerable degree of compliance. Based on an analogy between electrical and hydraulic nets, several models of the coronary circulation have been developed (see the work of [8,25,32] and references therein), including also autoregulation mechanisms which operate when the equilibrium of the biological system is disturbed, giving results in good agreement with the behavior of the natural system. Zero-dimensional and one-dimensional models cannot account for the fluid dynamics of the system in terms of local quantities, but they can provide the boundary conditions for the limited three-dimensional domain considered.…”