A New Approach for an Epicardial Cardiac Assist Device

Background: To date, the only option for patients with severe heart failure is transplantation. Although great advances in cardiac assist devices (CaAD) in recent years, none of them offers a permanent treatment option. The consequences of direct blood contact forbid a long-term use. To avoid this we have developed a new approach for a cardiac support system. We use an artificial muscle based on a dielectric elastomer membrane, offering direct epicardial support in systole and diastole. The aim of this work was to measure the maximum performance characteristics of an epicardial CaAD in an experimental setup. With these results we determine the effectiveness of the new CaAD in treating insufficient hearts using a FE computer simulation for rat hearts.

Method: Measurements were performed on a simplified model of an epicardial CaAD in which a silicone membrane was used as a dielectric elastomer actuator and enclosed a half-shell-shaped chamber. Voltage was continuously increased while pressure changes in the chamber were measured. Measurements were performed at various pre-stretching of the membrane. Each measurement was repeated eight times and the mean value was shown with standard deviation. To validate the effectiveness of the epicardial CaAD system, the measured pressure maxima were used to support insufficient rat hearts with restrictive cardiomyopathy using an FEM computer simulation.

Results: An exponential dependence of the maximum force development on the electrical voltage used was measured. This was all the greater, the more pronounced the pre-stretching of the membrane used. An optimum effect could be achieved with a pre-stretching of 230% and a voltage of 12 kV, resulting in a maximum pressure difference of 45 mm Hg (±4.5). The reaction time until the maximum pressure was reached averaged 25 milliseconds (±4.6). Using FEM-simulation, a restrictive cardiomyopathy with a fibrosis rate of 50% showed a significant reduction in cardiac function from EF 64% to 41%. Calculations result in a necessary pressure support of 53.2 mm Hg to normalize cardiac function. Support with 45 mm Hg leads to an increase in EF up to 61% and a normalization of end-diastolic pressure.

Conclusion: For the first time we were able to demonstrate the functionality of a new elastomer-based pump that can be used as an epicardial CaAD system. FEM simulation tests show a significant improvement of the heart function using the new pump for the treatment of heart failure.

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Artikel online veröffentlicht:
03. Februar 2022