Abstract 15121: Bioresorbable Molybdenum Electrodes: Towards a Novel Generation of Temporary Epicardial Pacing Wires

Abstract

Introduction: Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Removal is recommended on day 4-7. Occasionally, TEPW cannot be mechanically extracted, have to stay in the thorax and may rarely cause serious complications like migration and infection. We aim to develop novel, bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. Methods and Results: We manufactured prototypical braided molybdenum (Mo) leads (16 Mo wires of 40 μM diameter each, length 18 cm for ex-vivo, 7.5 cm for in-vivo trials) coated with the biodegradable polymers poly(lactide-co-glycolic acid) (PLGA, inner coating) and polycaprolactone (PCL, outer coating) for shaping and electrical insulation. Mo electrodes showed similar pacing and sensing properties to conventional steel electrodes (Osypka) in Langendorff-perfused rat hearts, even with somewhat lower stimulation thresholds. In artificial body fluid at 37°C, polymer-coated Mo electrodes dissolved at a rate of 1.6 ± 0.3 μg/cm 2 ·d (n=5) compared to uncoated electrodes with 30.3 ± 0.8 μg/cm 2 ·d (n = 4, p < 0.001). Assessing apoptosis and necrosis in human cardiomyocytes and cardiac fibroblasts, we detected no toxicity at Mo concentrations up to 0.52 mM. To test Mo TEPW in vivo, we sutured them epicardially onto the anterior wall of hearts of female Wistar rats, led them out of the thorax and placed them in a subcutaneous pocket. We tested electrophysiological properties directly after implantation, after two weeks and one month. Mo electrodes showed similar pacing and sensing properties directly upon implantation and after two weeks. After one month, all but one pair of Mo electrodes were mechanically broken at their exit from the thorax, the site of assumedly highest mechanical stress. Conventional steel TEPW had similar electrical properties following implantation, after two weeks and one month with no signs of breakage. Conclusion: We demonstrate that Mo TEPW can feasibly be used for epicardial pacing in vivo for up to two weeks. These findings represent an important step in the development of bioresorbable TEPW as a novel and even safer approach to temporary epicardial pacing.