Fluid–structure interaction modelling of a positive-displacement Total Artificial Heart

Abstract

For those suffering from end-stage biventricular heart failure, and where a heart transplantation is not a viable option, a Total Artificial Heart (TAH) can be used as a bridge to transplant device. The Realheart TAH is a four-chamber artificial heart that uses a positive-displacement pumping technique mimicking the native heart to produce pulsatile flow governed by a pair of bileaflet mechanical heart valves. The aim of this work was to create a method for simulating haemodynamics in positive-displacement blood pumps, using computational fluid dynamics with fluid–structure interaction to eliminate the need for pre-existing in vitro valve motion data, and then use it to investigate the performance of the Realheart TAH across a range of operating conditions. The device was simulated in Ansys Fluent for five cycles at pumping rates of 60, 80, 100 and 120 bpm and at stroke lengths of 19, 21, 23 and 25 mm. The moving components of the device were discretised using an overset meshing approach, a novel blended weak–strong coupling algorithm was used between fluid and structural solvers, and a custom variable time stepping scheme was used to maximise computational efficiency and accuracy. A two-element Windkessel model approximated a physiological pressure response at the outlet. The transient outflow volume flow rate and pressure results were compared against in vitro experiments using a hybrid cardiovascular simulator and showed good agreement, with maximum root mean square errors of 15% and 5% for the flow rates and pressures respectively. Ventricular washout was simulated and showed an increase as cardiac output increased, with a maximum value of 89% after four cycles at 120 bpm 25 mm. Shear stress distribution over time was also measured, showing that no more than $$4.5\times 10^{-4}$$ 4.5 × 10 - 4 % of the total volume exceeded 150 Pa at a cardiac output of 7 L/min. This study showed this model to be both accurate and robust across a wide range of operating points, and will enable fast and effective future studies to be undertaken on current and future generations of the Realheart TAH.

Unveiling the future of cardiac care: advances in mechanical circulatory support

“…The Carmat TAH system incorporates a self-modulating feature that adjusts cardiac output based on the patient's activity level, providing a personalized response to varying physiological demands. Clinical trials of the device have shown promising results, with the first patient surviving for 75 days in December 2013 [56]. The development of the Carmat TAH was spearheaded by Dr. Alain Carpentier, a renowned French surgeon recognized as a pioneer in modern mitral valve repair [57].…”

Modeling Dynamics of the Cardiovascular System Using Fluid-Structure Interaction Methods

“…A study by Bornoff et al focused on the use of a total artificial heart (TAH) as a bridge to transplant device for end-stage biventricular heart failure patients [61]. The Realheart TAH, a four-chamber artificial heart, mimics the native heart's pumping technique using positive displacement and bileaflet mechanical heart valves.…”

Novel para-aortic cardiac assistance using a pre-stretched dielectric elastomer actuator

“…Cardiac assist devices have been introduced as bridge to transplantation because of the shortage of heart donors. More recently, the interest of these devices has shifted towards a destination strategy [ 1 , 2 ]. Nevertheless, cardiac assist devices as destination therapies are still unmet clinical needs [ 3 ].…”