A Novel Wireless Power Transmission System for Left Ventricular Assist Devices

Purpose
LVADs are high power rated implants requiring a percutaneous driveline. Driveline infections result in frequent hospital admissions and increased patient mortality. Previous wireless power solutions were ineffective as high power requirements resulted in receiver coil heating and subcutaneous tissue damage. We developed a novel wireless energy transmission system consisting of thin flexible coils (Figure 1). A novel pulsed radio frequency transmission protocol (PRFTP) was developed to harness the thermoregulatory capacity of tissue blood flow.

Methods
We compared PRFTP with an equivalent conventional continuous transmission protocol (CTP) in an anaesthetised porcine model. After ethical approval two twin coil systems were implanted subcutaneously in a porcine series (N=18). A resistive load of 50 Ω was used to represent the LVAD. A thermistor array (N=14, Figure 2) on the receiver coil recorded a thermal profile. At the end of each experiment the pig was euthanised. We compared PRFTP with CTP in the absence of blood flow to quantify the effect of tissue blood perfusion on receiver coil cooling.

Results
Tissue heating with PRFTP was less than equivalent CTP (mean delta change 1.2C vs 3.4C at 7.5W). Tissue heating was greater with both protocols during the cadaver stage confirming the significant cooling effect of blood flow.

Conclusion
Tissue heating during radio frequency energy transmission is minimised using a novel coil form factor with a programmable pulsatile energy protocol. Optimisation of PRFTP parameters with scalable coil architecture is a route to a wireless LVAD power solution.