Spotlight on S-ICD™ therapy: 10 years of clinical experience and innovation

Abstract

Subcutaneous ICD (S-ICD™) therapy has been established in initial clinical trials and current international guideline recommendations for patients without demand for pacing, cardiac resynchronization, or antitachycardia pacing. The promising experience in ‘ideal’ S-ICD™ candidates increasingly encourages physicians to provide the benefits of S-ICD™ therapy to patients in clinical constellations beyond ‘classical’ indications of S-ICD™ therapy, which has led to a broadening of S-ICD™ indications in many centres. However, the decision for S-ICD™ implantation is still not covered by controlled randomized trials but rather relies on patient series or observational studies. Thus, this review intends to give a contemporary update on available empirical evidence data and technical advancements of S-ICD™ technology and sheds a spotlight on S-ICD™ therapy in recently discovered fields of indication beyond ideal preconditions. We discuss the eligibility for S-ICD™ therapy in Brugada syndrome as an example for an adverse and dynamic electrocardiographic pattern that challenges the S-ICD™ sensing and detection algorithms. Besides, the S-ICD™ performance and defibrillation efficacy in conditions of adverse structural remodelling as exemplified for hypertrophic cardiomyopathy is discussed. In addition, we review recent data on potential device interactions between S-ICD™ systems and other implantable cardio-active systems (e.g. pacemakers) including specific recommendations, how these could be prevented. Finally, we evaluate limitations of S-ICD™ therapy in adverse patient constitutions, like distinct obesity, and present contemporary strategies to assure proper S-ICD™ performance in these patients. Overall, the S-ICD™ performance is promising even for many patients, who may not be ‘classical’ candidates for this technology.

Evaluation of subcutaneous implantable cardioverter-defibrillator performance in patients with ion channelopathies from the EFFORTLESS cohort and comparison with a meta-analysis of transvenous ICD outcomes

“…One of the key advantages of the S-ICD is avoiding lead complications. 10 Many channelopathy ICD recipients are young patients at risk of the long-term morbidities associated with intravascular leads with the added risks of lead extraction. 2 , 6 , 11 TV lead failure rates for leads implanted for 5 years range from 5% to 15% and may be as high as 40% for leads followed for 8 years.…”

Hybrid subcutaneous and transvenous approach for cardiac resynchronization defibrillator implant in a patient with congenital heart disease and tricuspid bioprosthetic

“…Although an S-ICD avoids these problems, the current technology lacks capability for pacing (until leadless pacemaker communication is available) and particularly for CRT. 2 Different subcutaneous shock pathways other than the currently available technology have been previously explored. An anteroposterior pathway with a single posterior subcutaneous coil and inframammary can location was 93% successful in achieving defibrillation.…”

The subcutaneous ICD for prevention of sudden cardiac death: Current evidence and future directions

“…There is ongoing discussion, similar to the early experience with transvenous ICDs, whether defibrillation testing is necessary in all S-ICD recipients. 30 In contrast to transvenous ICDs, however, there are currently no randomized controlled studies like the SIMPLE 31 or NORDIC 32 trials available indicating that shock testing can also be foregone in S-ICD recipients. Until results of the prospective randomized PRAETORIAN-DFT trial 33 are available, it seems reasonable that S-ICD recipients generally undergo shock testing.…”

“…[37][38][39] This notwithstanding, especially patients with Brugada syndrome pose a challenge for current S-ICD systems; diligent screening, implantation, and follow-up are required to reduce the inherently elevated risk of inappropriate shocks in these individuals. 30 Available data from UNTOUCHED also indicate that expert programming and optimal implantation techniques are crucial in order to achieve this level. Indeed, the increased risk of inappropriate shocks F I G U R E 2 Examples of S-ICD implantations.…”