The Entirely Subcutaneous Implantable Cardioverter-Defibrillator: Initial Clinical Experience in a Large Dutch Cohort
How safe and effective is the subcutaneous implantable cardioverter-defibrillator (S-ICD)?
This was a retrospective review of 118 patients (mean age 50 years) who underwent implantation of a S-ICD for primary or secondary prevention of sudden death. Defibrillation testing was performed at least once at 65 J. Shock therapy was programmed at 80 J. The patients were seen at regular intervals in an outpatient clinic during a mean follow-up of 18 months.
Four patients had nine episodes of sustained ventricular tachycardia (VT), and another four patients had 36 episodes of ventricular fibrillation (VF) during follow-up. The first S-ICD shock was successful in restoring sinus rhythm in 98% of episodes. In one episode of VT, the shock resulted in acceleration of the VT followed by spontaneous termination. An inappropriate shock caused by T-wave oversensing, double-counting due to a new bundle branch block, electrical noise sensing, myopotential sensing, or atrial flutter occurred in 15 patients (13%). Fourteen percent of patients had a major complication, most commonly infection (5.9%), subcutaneous lead dislodgement (2.5%), premature battery depletion (1.7%), and skin erosion (1.7%).
The authors concluded that the S-ICD is highly efficacious for detecting and terminating VT/VF, but is associated with a relatively high risk of major complications.
The S-ICD has obvious advantages over conventional ICDs, but is not capable of antitachycardia pacing, long-term antibradycardia pacing, or cardiac resynchronization therapy. The 13% prevalence of inappropriate shocks is similar to the prevalence with transvenous ICDs, and probably will decrease as software refinements are instituted. The high infection rate is a concern, but probably also will decline as operator experience with the implantation process increases.
Keywords: Prevalence, Defibrillators, Follow-Up Studies, Heart Block, Ventricular Fibrillation, Electric Countershock, Bundle-Branch Block, Cardiac Resynchronization Therapy, Tachycardia
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