Two-Year Safety and Efficacy of the S-ICD | Journal Scan

Study Questions:

What is the safety and efficacy of the totally subcutaneous implantable cardioverter-defibrillator (S-ICD)?


Patient data were pooled from the IDE (S-ICD System IDE Clinical Investigation) and EFFORTLESS (Boston Scientific Post Market S-ICD Registry) studies. Shocks and complications were analyzed.


A total of 882 patients were followed for 651 ± 345 days. One hundred and eleven spontaneous episodes of ventricular tachyarrhythmia were treated in 59 patients. One hundred (90%) episodes were terminated with one shock and 109 (98.2%) within the 5 available shocks. Estimated 3-year inappropriate shock rate was 13%. Estimated 3-year mortality was 4.7%. Complications occurred in 11% of patients at 3 years. Three devices were replaced due to the need for ventricular pacing. Six-month complication rate decreased with each quartile of enrollment (Q1: 8.9%; Q4: 5.5%). There was also a trend toward a reduction in inappropriate shock (Q1: 6.9; Q4: 4.5%).


The authors concluded that S-ICD is safe and effective. Complications and inappropriate shocks can be reduced with operator experience and improved programing.


The advantages of the totally subcutaneous ICD include elimination of complications related to venous access, no need for fluoroscopy during implantation, no physical stress on leads associated with cardiac motion, less morbidity associated with device extraction, and a potential reduction in endovascular infection risk to patients with dialysis access or endovascular prostheses. The present study offers some assurance that S-ICD is safe and effective at least up to 3 years. Introduction of dual zone programing during the study period resulted in welcome reduction in inappropriate shocks to the levels more in line with transvenous ICDs. The present study stands out among other ICD trials in terms of its very low mortality rate of 1.6% annually. This is much less than in most primary prevention trials. It is therefore even more surprising given that almost one third of patients in the current study received S-ICDs for secondary prevention. I suppose this is reflecting the fact that patients in the current study are younger, more active, and perhaps healthier (by definition none of them required pacing). Of note, no study to date has directly compared the transvenous and totally subcutaneous ICD.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Nuclear Imaging

Keywords: Arrhythmias, Cardiac, Defibrillators, Defibrillators, Implantable, Fluoroscopy, Heart Failure, Heart Ventricles, Morbidity, Mortality, Primary Prevention, Registries, Safety, Secondary Prevention, Shock, Tachycardia, Ventricular, Ventricular Fibrillation

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