In-vivo Study of Cardiac Pressure-Volume Curves using Implantable RF Telemetry

We present our study of a real-time monitoring methodology of pressure-volume (PV) in-vivo signals generated by our implantable RF telemetry system, where the dual PV sensor is implanted in a heart of a freely moving animal subject. I. THE STUDY OVERVIEW Real-time left ventricular (LV) pressure-volume (PV) loops are one of the main indicators of the myocardium health in animals and humans. Accurate real-time PV data allow researchers to quantify cardiac pathology, e.g., congestive heart failure [1]. Thus, a small catheter that incases both pressure and volume sensors is implanted into the LV of the subject’s heart where the real-time measurements are taken. While blood pressure measurement using MEMS sensors is already established methodology, the blood volume measurements based on conductance catheter methodology is still subject of vigorous theoretical and experimental research [2]. Our system architecture consists of four system level blocks that share a common data and DC power bus: power regulating electronics, signal processing and control unit, RF transceiver, PV sensor interface, and the dual PV sensor itself (provided by Transonic Scisense Inc.). The complete system is encapsulated in a 3D printed custom bio-compatible package suitable for the surgical procedure. Size of the complete wireless PV telemetry system, including the Li–Poly battery, is (15× 15× 11)mm and it weighs 4.0g [4]. The PV wireless telemetry system was evaluated in–vivo using a 60kg swine subject. The study was designed to evaluate the PV system in a non–anaesthetised test subject, i.e., freely moving animal. In addition, the study was completed to evaluate catheter-heart interaction. Prior to surgery, the implant and PV catheter were sterilized. The catheter was inserted into the left ventricle via the carotid artery and the system was implanted and secured in the neck region of the test subject, Fig. 1a. Fluoroscopy was used to assist in the positioning of the catheter and implant within the left ventricle and neck region, Fig. 1b. Data was collected for 48 hours via the RF link from the implant to an external laptop. The implant is designed to transmit raw voltages, thus additional data processing *This work was supported by Transonic London ON, OCE, NSERC, CFI, and CMC Microsystems, Canada. The work was done at Western University Canada, tin accordance with ethics protocol AUP Number: 2014-003 1 ECE, Western University, Canada kfricke@uwo.ca 2 ENSEA/University Cergy-Pontoise/CNRS, France 3 Animal Care and Veterinary Services, Western University, Canada 4 Transonic Scisense Inc., Canada (a) (b) Implant