Outcomes for US Adoption of the Subcutaneous ICD
What has been the early experience with the totally subcutaneous implantable cardioverter-defibrillator (S-ICD) in the United States, and how do in-hospital outcomes among patients undergoing S-ICD compare with transvenous (TV)-ICD implantation?
This was a retrospective analysis of the National Cardiovascular Data Registry ICD Registry. A 1:1:1 propensity-matched analysis of 5,760 patients was performed to compare in-hospital outcomes among patients with S-ICD with those of patients with single-chamber (SC)–ICD and dual-chamber (DC)–ICD.
Among the 393,734 ICD implants, 3,717 were S-ICDs (0.9%). About 28% of the patients were female; the mean age was 67 years. Compared with SC-ICD and DC-ICD recipients, those with S-ICDs were more often younger, female, black, undergoing dialysis, and had experienced prior cardiac arrest. Among 2,791 patients with S-ICD who underwent defibrillation threshold (DFT) testing, 92.7%, 94.2%, 94.4%, and 99.7% were successfully defibrillated (≤65, ≤70, ≤75, and ≤80 J, respectively). In the propensity-matched analysis of 5,760 patients, in-hospital complication rates associated with S-ICDs (0.9%) were comparable to those of SC-ICD (0.6%) and DC-ICD rates (1.5%). Mean length of stay after S-ICD implantation was comparable to that after SC-ICD implantation and less than after DC-ICD implantation.
The authors concluded that the early adoption has been associated with low complication rates and high rates of successful DFT testing despite frequent use in patients with a high number of comorbidities.
The S-ICD has emerged as a major advance in the ICD technology, which now does not require endovascular instrumentation. It has been hypothesized that lead complications could be greatly reduced with the S-ICD, and that the infectious risk could be diminished. The significant limitation of the currently available S-ICD is its inability to pace for bradycardia or pace terminate ventricular tachycardia (VT), which may be an effective and painless treatment of up to 80% monomorphic VTs. At the time of study censorship in March 2015, almost 2% of ICD implants reported in the registry were S-ICDs. The authors provide a great deal of granular data about how the S-ICD implants differed from the traditional TV-ICDs up to the point of hospital discharge (i.e., the manuscript does not provide long-term clinical outcome data. It is concerning that only about 70% of S-ICD implants were performed with DFT testing, despite the lack of clinical trial data supporting the abandonment of this practice for S-ICDs. A note should be made of the fact that a randomized clinical trial of S-ICDs and TV-ICDs has not been completed.
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