Hemodynamic characterization of the Realheart® total artificial heart with a hybrid cardiovascular simulator.

BACKGROUND: Heart failure is a growing health problem worldwide. Due to the lack of donor hearts there is a need for alternative therapies, such as total artificial hearts (TAHs). The aim of this study is to evaluate the hemodynamic performance of the Realheart® TAH, a new 4-chamber cardiac prosthesis device. METHODS: The Realheart® TAH was connected to a hybrid cardiovascular simulator with inflow connections at the left/right atrium, and outflow connections at the ascending aorta/pulmonary artery. The Realheart® TAH was tested at different pumping rates and stroke volumes. Different systemic resistances (20.0-16.7-13.3-10.0 Wood units), pulmonary resistances (6.7-3.3-1.7 Wood units), and pulmonary/systemic arterial compliances (1.4-0.6 ml/mm Hg) were simulated. Tests were also conducted in static conditions, by imposing predefined values of preload-afterload across the artificial ventricle. RESULTS: The Realheart® TAH allows the operator to finely tune the delivered flow by regulating the pumping rate and stroke volume of the artificial ventricles. For a systemic resistance of 16.7 Wood units, the TAH flow ranges from 2.7 ± 0.1 to 6.9 ± 0.1 L/min. For a pulmonary resistance of 3.3 Wood units, the TAH flow ranges from 3.1 ± 0.0 to 8.2 ± 0.3 L/min. The Realheart® TAH delivered a pulse pressure ranging between ~25 mm Hg and ~50 mm Hg for the tested conditions. CONCLUSIONS: The Realheart® TAH offers great flexibility to adjust the output flow and delivers good pressure pulsatility in the vessels. Low sensitivity of device flow to the pressure drop across it was identified and a new version is under development to counteract this.

Video-based valve motion combined with computational fluid dynamics gives stable and accurate simulations of blood flow in the Realheart total artificial heart.

BACKGROUND: Patients with end-stage, biventricular heart failure, and for whom heart transplantation is not an option, may be given a Total Artificial Heart (TAH). The Realheart® is a novel TAH which pumps blood by mimicking the native heart with translation of an atrioventricular plane. The aim of this work was to create a strategy for using Computational Fluid Dynamics (CFD) to simulate haemodynamics in the Realheart®, including motion of the atrioventricular plane and valves. METHODS: The accuracies of four different computational methods for simulating fluid-structure interaction of the prosthetic valves were assessed by comparison of chamber pressures and flow rates with experimental measurements. The four strategies were: prescribed motion of valves opening and closing at the atrioventricular plane extrema; simulation of fluid-structure interaction of both valves; prescribed motion of the mitral valve with simulation of fluid-structure interaction of the aortic valve; motion of both valves prescribed from video analysis of experiments. RESULTS: The most accurate strategy (error in ventricular pressure of 6%, error in flow rate of 5%) used video-prescribed motion. With the Realheart operating at 80 bpm, the power consumption was 1.03 W, maximum shear stress was 15 Pa, and washout of the ventricle chamber after 4 cycles was 87%. CONCLUSIONS: This study, the first CFD analysis of this novel TAH, demonstrates that good agreement between computational and experimental data can be achieved. This method will therefore enable future optimisation of the geometry and motion of the Realheart®.