Implant and Midterm Outcomes of the S-ICD Registry

Study Questions:

What is the rate of complications and inappropriate shocks associated with subcutaneous implantable cardioverter-defibrillators (S-ICDs)?


Data for this study were obtained from an international registry of 985 patients (mean age 48 years) who received an S-ICD (primary prevention in 65%) and were followed for a mean of 3.1 years. The study endpoints were the complication rates at 30 and 360 days post-implantation and the rate of inappropriate shocks.


The complication rate was 4.1% at 30 days and 8.4% at 360 days. The most frequent complications were infection requiring device explantation (2.4%), erosion (1.7%), and inappropriate shocks due to oversensing (1.1%). During the 3.1 years of follow-up, the S-ICD was exchanged for a conventional ICD in 1.3% of patients because of the need for antitachycardia pacing (ATP), resynchronization therapy, or bradycardia pacing. Inappropriate shocks occurred during the first year of follow-up in 8.1% of patients and during the mean of 3.1 years of follow-up in 11.7%. Appropriate shocks occurred in 5.8% of patients at 1 year and in 13.5% by 5 years of follow-up. The cardioversion success rate was 97.4%.


The safety and efficacy of the S-ICD compare favorably with those of conventional ICDs.


Exclusion criteria for the S-ICD include monomorphic ventricular tachycardia treatable by ATP and clinically significant bradyarrhythmias. This explains the low incidence of these events during follow-up. The rate of inappropriate shocks is in line with that of conventional ICDs, indicating that the S-ICD atrial fibrillation/supraventricular tachycardia detection algorithms are fairly accurate even in the absence of intracardiac leads.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Bradycardia, Cardiac Resynchronization Therapy, Defibrillators, Implantable, Electric Countershock, Outcome Assessment (Health Care), Primary Prevention, Secondary Prevention, Shock, Tachycardia

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