Towards a Wireless Pacing System for Vascular Implantation
Over 1 million patients are implanted annually with a pacemaker for the treatment of cardiac arrhythmias and conduction disorders. However, despite numerous advancements in pacemaker technology, lead-related complications associated with these devices continue to compromise patient safety and survival. Wireless power transfer holds great promise for improving health outcomes in biomedical implants such as the pacemaker. However, efficient power transfer and effective operational range have remained a challenge within anatomical constraints. In this work, we demonstrated an intravascular, wirelessly-powered, batteryless, microscale pacer deployed to the anterior cardiac vein (ACV). First, we employed a novel intermittent transmission remote-control architecture with improved power efficiency to enable sufficient power transfer without compromising on Specific Absorption Rate (SAR). We then integrated this architecture into a 3-tiered, 2-sub-system, 4-coil design, which operates on two different frequencies. Our pacemaker was designed to achieve wireless power transfer over a 55 mm range from an external transmitter to an intravascular receiver. A charging sub-system was designed to transmit power over 25 mm using inductive power transfer to a subcutaneous receiver, which then charged a battery feeding the transmitter of a stimulation sub-system. We then introduced a stimulator circumferentially confined to a 3 mm diameter hollow-cylinder that delivered >5 V using wireless power transfer at 13.56 MHz, with over 20 mm transmitter-receiver displacement between the subcutaneous unit and pacer unit. Further validation was performed using Finite Element Method (FEM) simulation of the cardiac cycle, guided by anatomical variations established by Magnetic Resonance Images (MRI). Finally, we demonstrated the capacity for both ex vivo and in vivo pacing of pig hearts following pacer deployment in the ACV. This introduced, for the first time, the unprecedented capacity for wireless intravascular pacing with potential for multi-organ stimulation. Thus, the proposed system design has the potential to bypass the multitude of complications associated with pacemaker wires, repeated procedures for battery replacement, and mechanically burdened fixation mechanisms.