Molybdenum Temporary Epicardial Pacing Wires: Function and Degradation

Maria-Elisa Prieto Jarabo (Dresden)1, C. Redlich (Dresden)2, A. Schauer (Dresden)3, C. Guder (Dresden)2, G. Poehle (Dresden)2, T. Weißgärber (Dresden)2, V. Adams (Dresden)3, U. Kappert (Dresden)4, A. El-Armouche (Dresden)5, A. Linke (Dresden)6, M. Wagner (Dresden)7

1Herzzentrum Dresden GmbH an der TU Dresden Klinik für Innere Medizin und Kardiologie Dresden, Deutschland; 2Fraunhofer IFAM Institut für Fertigungstechnik und angewandte Materialforschung Dresden, Deutschland; 3Medizinische Fakultät Carl Gustav Carus der TU Dresden Labor für Molekulare und Experimentelle Kardiologie Dresden, Deutschland; 4Herzzentrum Dresden GmbH an der TU Dresden Klinik für Herzchirurgie Dresden, Deutschland; 5Medizinische Fakultät Carl Gustav Carus der TU Dresden Institut für Pharmakologie und Toxikologie Dresden, Deutschland; 6Herzzentrum Dresden GmbH an der TU Dresden Klinik für Innere Medizin, Kardiologie und Intensivmedizin Dresden, Deutschland; 7Herzzentrum Dresden GmbH an der TU Dresden Rhythmologie Dresden, Deutschland


Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Wires typically begin to fail around postoperative day four and are extracted. Occasionally, TEPW cannot be mechanically removed, have to stay in the thorax and may rarely cause serious complications like migration and infection. We aim to develop novel, bioresorbable TEPW which will dissolve over time, even if postoperative removal is unsuccessful. 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 experiments) 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 as conventional steel electrodes (Osypka) in Langendorff-perfused rat hearts, even with somewhat lower stimulation thresholds. In artificial body fluid at 37°C, the polymer-coated Mo electrodes dissolved at a Mo release rate of 1.6 ± 0.3 µg/cm2·d (n=5) compared to uncoated electrodes with 30.3 ± 0.8 µg/cm2·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 the in vivo properties of Mo TEPW, we sutured them epicardially onto the anterior wall of the heart of female Wistar rats, led them out of the thorax through an intercostal space and placed them in a subcutaneous pocket. Electrophysiological properties were tested directly after implantation and after different periods of time. Mo electrodes showed similar pacing and sensing properties directly upon implantation and after two weeks, with only impedance and slew rate of the sensed R-wave decreasing time-dependently. After one month, all but one pair of Mo electrodes were mechanically broken at their exit from the thorax, the site of the assumedly highest mechanical stress. Progressive Mo degradation led to multiple fragmentation of the Mo TEPW after six months. The conventional steel TEPW we used as control had similar electrical properties directly after implantation, after two weeks and after one month, without signs of broken electrodes. After six months, all but one pair of steel electrodes were mechanically broken at their exit from the thorax. We demonstrate that Mo TEPW can feasibly be used for epicardial pacing in vivo for up to two weeks and observed the progress of Mo degradation up to six months. These findings represent an important step in the development of bioresorbable TEPW as a novel and even safer approach to temporary epicardial pacing.
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