The clinical promise of the subcutaneous implantable cardioverter-defibrillator (S-ICD System®; Boston Scientific, Natick, MA), the first ICD in which the leads are placed under the skin of the chest and are not connected to the heart or vasculature, was confirmed by longer-term (median of 22-month) safety and efficacy data reported in the April 28, 2015 issue of the Journal of the American College of Cardiology (JACC). The S-ICD was approved by the FDA in September 2012 to provide an electric shock to the heart (defibrillation) when the patient’s heart is beating chaotically (ventricular fibrillation) or abnormally fast (ventricular tachyarrhythmia). Because the S-ICD is not implanted in the vasculature or heart, major complications, such as device/lead displacement or failure and pneumothorax, are very rare. Because the S-ICD lacks pacing capacity, it is contraindicated in patients who require a pacemaker or pacing therapy. The JACC article, coauthored by MUSC cardiologist Michael Gold, M.D., Ph.D., is a pooled analysis of 882 patients implanted with the S-ICD who were either participants in the investigational device exemption (IDE) study that led to FDA approval or members of the European EFFORTLESS S-ICD registry, created to evaluate the long-term efficacy and safety of the S-ICD. Of the 111 events of ventricular fibrillation/tachyarrhythmia reported in the study, 90% (100) were terminated with one shock and 98% (109) within the five shocks available with the S-ICD. This is similar to reported shock termination rates with traditional ICDs. Device-related complications occurred in 11.1% of patients at three years, with generator pocket infections and inappropriate shocks due to oversensing being the more prominent. Rates of both decreased as providers gained experience with the S-ICD, infection control techniques were implemented, and dual zone programming was favored. The infection rate was reduced more than 3-fold in the latter half of these trials and supraventricular arrhythmias by about 70%. Improvement in this technology will occur in future iterations of the device that should be available in the summer of 2015. MUSC, the leading center in South Carolina for implantation of this device, participated in many of the early clinical studies that led to the approval of the S-ICD.
An MUSC blog
Update on the Subcutaneous ICD: How Is It Faring in the Clinic?