Abstract:
Heart failure is a global pandemic affecting 26 million people worldwide. Heart transplantation
remains the gold standard for patients with advanced heart failure (AHF) where surgical or
pharmaceutical intervention is unable to restore cardiac output. Unfortunately, the prevalence of
the disease grows while the number of available donor hearts remain constant. As an alternative,
mechanical circulatory support (MCS) systems are used to treat AHF, and there is a growing
demand for the application of MCS in destination therapy (DT) where the pump runs until patient
end-of-life. However, due to the high power requirements, current MCS systems rely on a
percutaneous driveline for power delivery. There is an ongoing risk of driveline infection (DLI)
which is particularly problematic for DT. Wireless power transfer by a transcutaneous energy
transfer (TET) system has been proposed as a solution to eliminate DLI.
Current generation MCS systems require 5 – 10 W of power and TET to meet this high power
requirement bring concerns with heating. Along with hermeticity requirements associated with
long-term implantation, the application of TET to DT remains a challenging topic. This thesis
addresses the issues with TET heating and develops a hermetic package suitable for chronic
implantation. In order to meet the safety limits recommended by international standards, the
specific absorption rate (SAR) of the system must be below 2 W/kg, the external device in contact
with skin must be below 41 °C, and the implant surface must not exceed 39 °C. A hermetically
sealed TET system was designed and numerical models utilising the Pennes bioheat transfer
equation determined that during the maximum power transfer to a 10 W load, the SAR was 5.6
mW/kg, the peak skin temperature was 39.5 °C, and the peak implant surface temperature was
38.9 °C.
The proposed TET system was fabricated and instrumented to measure system temperatures.
The instrumented system was implanted in an acute ovine experiment simulating power transfer
to 5 W and 10 W loads. The maximum surface temperatures of the primary and secondary coils
were 37.73 ± 0.20 °C and 38.31 ± 0.78 °C, respectively. The values were within the recommended
limits and in agreement with the numerical models. The TET system was integrated with the
Procyrion Aortix MCS system, and continuous operation as well as practical discharge cycles were
shown to be supported by the TET system without any interruptions to the pump function.
This thesis concludes by presenting a hermetically packaged TET system capable of meeting the
requirements of current generation MCS systems and addresses the major concerns with
temperature and long-term durability associated with the application of TET in MCS for DT.