Extracardiac Inappropriate Shocks in Subcutaneous Implantable Cardioverter Defibrillator: Management in Emergency Department

Background: The subcutaneous implantable cardioverter defibrillator (S-ICD) is an established treatment for the prevention of sudden cardiac death. In the S-ICD studies, inappropriate shocks (IAS) rate were reported to renge between 5% to 25% and to be mainly due to cardiac and noncardiac oversensing. Objective: This review highlights data on IAS complications of the S-ICD and is aimed to help in identifying the causes of extracardiac oversensing to facilitate safe and effective emergency management and to reduce the incidence of adverse outcomes. Methods: Literature between January 2010 and March 2020 on IAS and S-ICD was identified by database search. We included studies assessing IAS rates due to extracardiac oversensing. We identified 12 eligible articles including meta-analysis and 28 selected case reports. Results: The total population included 2654 reported patients. Of these, 84 patients received extracardiac IAS. The malfunction of S-ICD due to extracardiac oversensing was related, in particular, to myopotentials (34%) and electromagnetic interferences (29%). The meta-analysis demonstrates an overall high prevalence of extracardiac IAS of 22% (95% CI 8% - 50%); the prevalence was 6% (95% CI 3% - 12%) in patients without the SP (SMART-Pass) filter and 46% (95% CI 12% - 84%) in patients with the SP filter (P=0.047). Conclusion: Our findings show the high prevalence of extracardiac IAS in patients with S-ICD and demonstrated that the SP is unable to prevent the IAS due to extracardiac reasons. It is important in the Emergency Department for the appropriate management of IAS to identify the various causes.