Abstract Body (Do not enter title and authors here): Background: Heart-failure with preserved ejection fraction (HFpEF) now accounts for ~50% of heart-failure admissions and carries a 5-15% incidence of sustained ventricular tachycardia or fibrillation that can precipitate sudden cardiac arrest. Existing Holter monitors and implantable cardioverter-defibrillators are hindered by bulky form factors, finite batteries, and patient discomfort, limiting long term rhythm surveillance and timely intervention. A fully implantable, wireless and battery free platform that unifies high-fidelity electrocardiography (ECG) with on board stimulation using dual purpose electrodes could enable the study of cardiac function in a dynamic, unrestricted environment in freely moving murine models.

Methods and Result: A miniature, wireless cardiac monitor stimulator was engineered that harvested power at 13.56 MHz through a flexible Polyimide dual copper antenna. Eight stimulating and recording and one return gold electrode, encapsulated in parylene-C and 10:1 PDMS were purposed to capture intracardiac ECG while an infrared-addressable (940 nm) stimulation NEC protocol delivered closed-loop pacing. In vivo studies implant the device on adult murine ventricles in wild-type and diabetic-TAC HFpEF models. Following anesthesia with isoflurane, a thoracotomy was performed to expose the heart. The flexible device constructed using polyimide with two copper layers was placed directly on the heart. The device was dual-coated with Parylene-C, along with a thin layer of Silicone Elastomer (10:1) to ensure biocompatibility. Electrophysiological signals were recorded after stimulation was applied via the implanted microelectrodes. Preliminary results demonstrate the feasibility of WPT and functionality of the implant within a specified cage environment through load sweep and power harvesting characterization and stimulation capabilities (0.0136-3.3V). We have observed distinct patterns in the recorded data that differentiate between mice with induced cardiac arrhythmias and post stimulation signals. Ongoing studies are being conducted to record cardiac data from the electrodes and process the recorded data.

In summary, our study demonstrated the feasibility of using a flexible, wireless device to stimulate and record real-time cardiac electrophysiological data in freely moving murine models. While preliminary findings proved stimulation feasibility, ongoing studies will on recording from freely moving animals to understand cardiac dynamics.