In recent years, electrical driven mechanical circulatory assistance or replacement has become a viable treatment option not only for patients with end stage heart diseases, but also for the treatment of less sick patients. Used as a bridge to transplant or as a destination therapy, patient survival on device has increased significantly over the last years. However, infections and sepsis are still a major cause for adverse events and patient death in mechanical circulatory support. Over the years, the percutaneous line used for electrical power delivery has been repeatedly highlighted as a severe weak point, not only due to infections of the driveline exit site, but also as a source for mechanical failure or accidental mishandling by the patient.
In this work, a transcutaneous energy transfer system is developed. Here, electrical power is transmitted through the intact skin via an inductive link, consisting of an external and an implanted coil constituting an electrical transformer. Since the coils are not mechanicallyfixed, the electrical behavior of the transformer changes with inter coil geometry.
This changing behavior is modeled using simulation and numerical calculation tools. The results are used in a electrical system simulation including the surrounding power electronics needed to drive the inductive link. A new inverter principle is developed and theoretically compared to the prominent inverter topology. Both inverters are set up and measurement results are used to verify the simulation model and its results.
The load of the TET system is a pulsatile flow total artificial heart, the Reinheart TAH. Low electrical losses are considered crucial, in particular at the implanted components since electrical losses translate to heating of surrounding tissue. Additionally, in this implementation of the TET system, no outwards telemetry is needed to ensure safe operation. Instead, the simulation model is used to find an optimal geometry and turn number combination of the two coils, observing mechanical and voltage limits provided by the target systems of the total artificial heart and reducing losses occurring in all implanted components of the TET system.
The system is set up and tested on the bench in an artificial circulatory system simulator (mock loop). The results demonstrated that the voltage boundaries given by the target system are observed. Efficiencies of up to 87.5% at a peak output power of 45W were measured, excluding the losses of the supply voltage generation. In the mock loop test the supply losses were included and total system efficiencies of up to 75% were reached.
The system is used in an animal trial experiment measuring the temperature rise due to the interaction between the electromagnetic field and the tissue surrounding the coils. The results show that the temperature of the tissue surrounding the transmission coil does not exceed from that oft the core animal.
Therefore, it can be concluded that the manufactured system is able to safely deliver 45W to the target system of an artificial heart in vivo. The proposed simulation approach was verified and found suitable for the setup of a transcutaneous energy transfer system under predefined parameters of a target system, including coil sizes, output powers and output voltages.