Assessment of injury current during leadless pacemaker implantation
Introduction
Since the first pacemaker implantation in 1958, pacemaker technology to treat bradyarrhythmias has rapidly advanced and nearly one million devices are being implanted each year worldwide [1,2]. Despite technical improvements, transvenous pacemaker systems are associated with potential peri- as well as postprocedural complications such as pneumothorax, cardiac perforation, and venous obstruction [3,4]. In addition, chronic damage to the leads and the inherent risk of infection may lead to increased morbidity over time [5]. These issues have triggered the development of leadless pacemaker systems. The most widely implanted leadless pacemaker, the Micra Transcatheter Pacing System (Micra TPS, Medtronic, Minneapolis, MN), has a capsule-shaped body which is implanted directly into the right ventricle to offer VVI(R) pacing. The safety and efficacy has been demonstrated in a non-randomized, prospective study [6] and was confirmed in large retrospective registries [7,8].
Conventional transvenous pacemaker leads may be anchored to the right ventricle passively using tines (passive fixation leads) or via active fixation by a helix which is screwed into the myocardium (active fixation leads). The placement of both types of leads is traumatic to the tissue and causes local injury known as the “injury current” (IC) [[9], [10], [11]]. The IC is recorded at the site of implantation and is represented by a prolongation of the intracardiac electrocardiogram (EGM) and an elevation of the ST segment. Retrospective studies have shown an association between the presence of an IC and stable lead placement [9,10]. In active-fixation leads, the IC may be clearly visible because the helix is part of the cathode of the electrode; however, ICs can also be recorded in passive-fixation leads likely due to the local cellular pressure damage during implantation [12].
The Micra TPS device is anchored to the right ventricle by four self-expanding nitinol tines which are hooked into the myocardium [6]. Adequate pressure of the delivery catheter onto the myocardium is mandatory for satisfactory device positioning. It is, however, unclear whether local damage to the myocardial tissue, and therefore an IC, can readily be observed shortly after implantation of a leadless pacemaker. The current study was therefore designed to investigate the presence and relevance of an IC during implantation of a Micra TPS leadless pacemaker system.
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Study population
30 consecutive patients (26 patients at the University Hospital Zurich, 4 patients at the Cantonal Hospital Baden) undergoing 30 Micra TPS implantation between October 2019 and March 2020 in whom an intrinsic RV signal was assessable (excluding patients with complete AV block and no escape rhythm) were included. The study was approved by the local ethics committee (KEK-ZH-NR: 2020–00811). All enrolled patients provided written informed consent. The Micra TPS pacemaker was implanted according to
Study population and baseline characteristics
The mean age at implantation was 78 ± 12 years and 70% of the population were male (Table 1). Underlying cardiopathy was coronary artery disease in 30% of patients with an average left ventricular ejection fraction of 59 ± 8%. The underlying conduction abnormality resulting in device implantation was bradycardic atrial fibrillation or atrial fibrillation with complete atrioventricular block in 30% and sick sinus syndrome in 40% of the patients. 40% of the patients had experienced at least one
Discussion
The main observations from this study of 30 consecutive patients undergoing a routine Micra TPS implantation are:
- 1)
An injury current (IC) can be recorded in more than one-third of patients during the intervention.
- 2)
Its presence has an impact on the likelihood of immediate device repositioning due to higher initial capture thresholds.
- 3)
Clinically relevant device parameters like sensing and capture thresholds are similar at 2 weeks follow-up independent of the presence or absence of an IC at
Disclosures
AB has received consultant and/or speaker fees from Abbott, Bayer Healthcare, Biosense Webster, Biotronik, Boston Scientific, Bristol-Myers Squibb, Cook Medical, Daiichi Sankyo, Medtronic, Pfizer, and Spectranetics/Philipps.
AMS has received educational grant from Abbott, Bayer Healthcare, Biotronik, Biosense Webster, Bristol-Myers Squibb, Boston Scientific, Medtronic, and Pfizer. He reports stock of Gilead Sciences.
DH has received educational grants, speaker fees or fellowship support from
Funding sources
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Aknowledgements
None.
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