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End of service considerations The issues affecting a small number of Nanostim™ LCP devices serve as a reminder that there are certain unknowns surrounding leadless pacemaker technology. This is particularly true with reference to the best strategy when they reach the end of service. These devices have not been in use long enough for any meaningful data to be available on actual battery longevity or long-term complications. Successful retrieval has been demonstrated after a comparatively short duration of implantation, but success rates diminish the longer the device has been in. 16–18 Encapsulation over time can lead to greater difficulty retrieving the device. If the proximal retrieval button has been reached by the fibrous capsule, it may not be accessible, and the device may therefore have to remain in situ. 19 If retrieval is not possible, having a new leadless system alongside an old one has been shown to be feasible. The human RV can accommodate at least three Micra™ TPS devices simultaneously, seemingly without mechanical interaction between them in a reanimated cadaver heart, although the long-term implications of having that amount of hardware left permanently in the heart are unknown. 20 The arrival of leadless pacemaker technology represents an exciting development in cardiac pacing, with the potential to reduce complications by eliminating the need for leads and a pocket The future The restriction of leadless pacemakers to single-chamber ventricular pacing limits their use to a comparatively small subgroup of patients who require a pacemaker. Device companies will therefore be looking for ways to broaden the technology to enable dual chamber pacing, although this may yet be a long way off. In theory it should be possible to implant a separate device in the RA, perhaps with Bluetooth ® as a means of communication between it and the ventricular device, though fixation of the device in the thin-walled RA poses a greater challenge, and perhaps a higher risk of complications. Remote monitoring of atrial activity from the ventricular device to enable atrial tracking is also under investigation. If dual chamber leadless pacing becomes possible, then so might biventricular pacing, another natural progression for the application of this technology. As with an atrial device, however, the challenge beyond reliable continuous remote communication between the components, includes securing a device to References 1 Larsson B et al. Lessons from the first patient with an implanted pacemaker: 1958– 2001. Pacing Clin Electrophysiol 2003;26(1 Pt 1):114–24. 2 Aquilina O. A brief history of cardiac pacing. Images Paediatr Cardiol 2006; 8(2):17–81. 3 Cunningham D et al. National audit of cardiac rhythm management devices April 2015–March 2016. www.bhrs. com/files/files/Audit%20 Reports/CRM%20Devices%20 National%20Audit%20 Report%202015-16.pdf (accessed July 2018). 4 Mond HG, Proclemer A. The 11th world survey of cardiac pacing and implantable cardioverter-defibrillators: calendar year 2009 – a World Society of Arrhythmia’s project. Pacing Clin Electrophysiol 2011;34(8):1013–27. 5 Udo E et al. Incidence and predictors of short- and long-term complications in pacemaker therapy: The FOLLOWPACE study. Heart Rhythm 2012;9:728–35. 6 Sandoe JAT et al. Guidelines for the diagnosis, prevention and management of implantable cardiac electronic device infection. Report of a joint Working Party project on behalf of the British Society for Antimicrobial Chemotherapy (BSAC, host organisation), British Heart Rhythm Society (BHRS), British Cardiovascular Society (BCS), British Heart Valve Society (BHVS) and British Society for Echocardiography (BSE). J Antimicrob Chemother 2015; 70:325–59. 7 First implants made for Nanostim Leadless Pacemakers. www.dicardiology.com/content/ first-implants-made-nanostim- leadless-pacemakers (accessed July 2018). 8 Sideris S et al. Leadless cardiac pacemakers: Current status of a modern approach in pacing. He