The Subcutaneous Implantable Cardioverter Defibrillator

Abstract

The subcutaneous implantable cardioverter defibrillator (S-ICD) is a subcutaneous alternative to conventional transvenous ICD (TV-ICD) systems, which have previously been shown to treat life-threatening ventricular tachyarrhythmias in cardiac disease patients. A review of the literature reveals that S-ICDs have similar shock efficacy rates for both induced and spontaneous ventricular tachyarrhythmias when compared with TV-ICDs. Furthermore, S-ICDs seem to have a higher specificity for withholding therapy when supraventricular tachycardia is present compared with TV-ICDs. The advantages of the S-ICD system are numerous: fewer vascular complications including thrombosis and hemothorax, avoidance of fluoroscopy, and an easier means of lead replacement. These advantages make the S-ICD system most suitable for younger patients who may require replacements in later life, those with abnormal venous anatomy, and individuals prone to infection and/or central vein thrombosis. However, S-ICDs are not without their complications and are associated with a higher incidence of inappropriate shocks secondary to T wave oversensing. S-ICDs also lack antitachycardia pacing, making them a suboptimal device in patients with recurrent monomorphic ventricular tachycardia who would otherwise benefit from the antitachycardia pacing offered in TV-ICDs. Lastly, the limited number of long-term randomized, head-to-head studies involving direct comparison with TV-ICDs poses a challenge in the implementation of the S-ICD.

Subcutaneous implantable cardioverter‐defibrillator in primary and secondary prevention of sudden cardiac death: A meta‐analysis

“…One of the main reasons for S‐ICD development was to avoid complications associated with electrodes/leads such as insulation defects, fractures, losses of ventricular capture, movements, etc . Our results confirm the differences in electrodes/leads complications between S‐ICD and TV‐ICD.…”

“…However, the S‐ICD has its own limitations. In contrast to the TV‐ICD, S‐ICD lacks pacing capacity and therefore cannot provide anti‐tachycardia pacing, anti‐bradycardia, and resynchronization therapy . For these reasons, it is relevant to compare the effectiveness and safety of both devices.…”

“…The most commonly used transvenous ICD (TV‐ICD) is associated with complications related to intracavitary electrodes, both perioperative and long term. To address this problem, subcutaneous ICD (S‐ICD) was developed . S‐ICD is entirely extravascular and avoids introduction of electrodes and leads into the cardiac cavities and venous system and, therefore, lead‐related complications.…”

Efficacy and safety of the subcutaneous implantable cardioverter defibrillator: a systematic review

“…However, many of these reports stem from single centres and include small patient numbers. A few reviews of the S-ICD system have evaluated many of these studies 5 6 7 but do not pool clinical outcomes. We reviewed current evidence supporting the use of S-ICD devices from primary evaluations of efficacy and safety outcomes.…”