LAUSR

An 82-year-old female with history of complete heart block diagnosed in 2009 presented for upgrade of her MICRA VR (Medtronic Inc., Minneapolis, USA) pacemaker to an AV (atrioventricular) MICRA. Her initial dual-chamber transvenous pacemaker experienced right ventricular (RV) lead fracture from subclavian crush injury in 2016. This was extracted and replaced with a new right-sided CRT-P. One year later, she experienced another crush injury to her RV lead, prompting placement of an additional RV lead. In 2018, she presented with presyncope due to intermittent failure to capture from the RV lead and underwent complete system removal and MICRA VR implantation. She subsequently re-presented with progressive fatigue and dyspnea. Echocardiogram in March 2020 demonstrated unchanged LV ejection fraction (40–45%) with AV dys-synchrony. Upon FDA approval of MICRA AV, an upgrade to an AV device was offered to the patient. During implant, three suitable inferior-mid septal pacing locations were tested. Despite low output 0.25 V at 0.24 ms pacing stimuli, the MICRA VR inhibited pacing when VVI and was turned VOO during implant. There was no mechanical artifact from MICRA VR noted on MICRA AV sensing, with reliable A4 tracking in VDD. Her pre-existing device was turned off and not extracted (Fig. 1). When faced with device revision or upgrade of leadless pacemakers, options include implantation of a transvenous system while leaving the MICRA in situ or extraction of the old MICRA (though this presents increased procedural challenges as time passes due to device endothelialization) [1]. Alternatively, a new MICRA can be implanted while keeping the old device in situ, but concern has been raised about multiple cardiac devices causing mechanical interference [2]. We demonstrate that MICRA AV can be easily implanted in close proximity to a pre-existing disabled MICRA VR, including testing multiple pacing sites for optimal threshold, with intact VDD function after turning MICRA VR off.