A worldwide experience of the management of battery failures and chronic device retrieval of the Nanostim leadless pacemaker

BACKGROUND The Nanostim leadless pacemaker (LP) met the primary endpoints in an investigational device exemption trial, and was shown to be fully retrievable percutaneously. In October 2016, St Jude Medical issued a worldwide alert of a battery malfunction that caused lost pacing output and LP communication. OBJECTIVE To report the battery failure mechanism and incidence and the worldwide patient management, including device retrieval experiences. METHODS The affected LP battery is a custom lithium-carbon monofluoride cell. These were returned after failure and underwent analysis assessing electronics and battery performance. Data were collected in ongoing clinical studies when LPs were abandoned or retrieved. RESULTS Of 1423 LPs implanted worldwide, there were 34 battery failures, occurring at 2.9 +/- 0.4 years with no instances of associated patient injury. Analysis of returned batteries revealed an increase in battery resistance caused by insufficient electrolyte availability at the cathode/anode interface. A total of 66 of 73 retrieval attempts were successful (90.4%; implant duration range: 0.2-4.0 years). The LP docking button was inaccessible in 6 patients, and the docking button detached from the LP during retrieval in 1 patient. There was 1 case of arteriovenous fistula and another case of the LP docking button migrating into the pulmonary artery. There were also 115 non-LP retrieval patients after the advisory who received an additional pacemaker, with no adverse device-to-device interactions reported. CONCLUSION As with standard pacers, LPs can have critical battery failures. Chronic retrieval of LPs is safe and efficacious.