The Carmat bioprosthetic total artificial heart (C-TAH) is a biventricular pump developed to minimize drawbacks of current mechanical assist devices and improve quality of life during support. This study aims to evaluate the safety of the hybrid membrane, which plays a pivotal role in this artificial heart. We investigated in particular its blood-contacting surface layer of bovine pericardial tissue, in terms of mechanical aging, risks of calcification, and impact of the hemodynamics shear stress inside the ventricles on blood components. Hybrid membranes were aged in a custom-designed endurance bench. Mechanical, physical and chemical properties were not significantly modified from 9 months up to 4 years of aging using a simulating process. Exploration of erosion areas did not show no risk of oil diffusion through the membrane. Blood contacting materials in the ventricular cavities were subcutaneously implanted in Wistar rats for 30 days as a model for calcification and demonstrated that the in-house anti-calcification pretreatment with Formaldehyde-Ethanol-Tween 80 was able to significantly reduce the calcium concentration from 132 μg/mg to 4.42 μg/mg (p < 0.001). Hemodynamic simulations with a computational model were used to reproduce shear stress in left and right ventricles and no significant stress was able to trigger hemolysis, platelet activation nor degradation of the von Willebrand factor multimers. Moreover, explanted hybrid membranes from patients included in the feasibility clinical study were analyzed confirming preclinical results with the absence of significant membrane calcification. At last, blood plasma bank analysis from the four patients implanted with C-TAH during the feasibility study showed no residual glutaraldehyde increase in plasma and confirmed hemodynamic simulation-based results with the absence of hemolysis and platelet activation associated with normal levels of plasma free hemoglobin and platelet microparticles after C-TAH implantation. These results on mechanical aging, calcification model and hemodynamic simulations predicted the safety of the hybrid membrane used in the C-TAH, and were confirmed in the feasibility study.

Heart failure is a progressive and often fatal pathology among the main causes of death in the world. An implantable total artificial heart (TAH) is an alternative to heart transplantation. Blood damage quantification is imperative to assess the behavior of an artificial ventricle and is strictly related to the hemodynamics, which can be investigated through numerical simulations. The aim of this study is to develop a computational model that can accurately reproduce the hemodynamics inside the left pumping chamber of an existing TAH (Carmat‐TAH) together with the displacement of the leaflets of the biological aortic and mitral valves and the displacement of the pericardium‐made membrane. The proposed modeling workflow combines fluid–structure interaction (FSI) simulations based on a fixed grid method with computational fluid dynamics (CFD). In particular, the kinematics of the valves is accounted for by means of a dynamic mesh technique in the CFD. The comparison between FSI‐ and CFD‐calculated velocity fields confirmed that the presence of the valves in the CFD model is essential for realistically mimicking blood dynamics, with a percentage difference of 2% during systole phase and 13% during the diastole. The percentage of blood volume in the CFD simulation with a shear stress above the threshold of 50 Pa is less than 0.001%. In conclusion, the application of this workflow to the Carmat‐TAH provided consistent results with previous clinical studies demonstrating its utility in calculating local hemodynamic quantities in the presence of complex moving boundaries.

Total Artificial Heart (TAH) represents the only valid alternative to heart transplantation, which number is continuously increasing in recent years. The Carmat-TAH, example of a modern generation of TAH, is a biventricular pulsatile, electrically powered, hydraulically actuated flow pump with all components embodied in a single device. One of the major issues for TAHs is the washout capability of the device, strictly correlated to the presence of blood stagnation sites. The aim of this work is to develop a numerical methodology to study the washout coupled with the fluid dynamics evaluation of the Carmat-TAH during nominal working conditions. The first part of this study, focussed on the CT scan analysis of the hybrid membrane kinematics during TAH operation which was replicated with a fluid-structure interaction simulation in the second part. The difference in percentage between the in-vitro and in-silico flow rates and stroke volume is 9.7% and 6.3%, respectively. An injection of contrast blood was simulated, and its washout was observed and quantified with the volume fraction of the contrast blood still in the ventricle. The left chamber of the device showed a superior washout performance, with a contrast volume still inside the device after four washout cycles of 6.2%, respect to the right chamber with 15%.

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