The Entirely Subcutaneous Defibrillator - A New Generation and Future Expectations

Subcutaneous versus transvenous implantable cardioverter defibrillator in hypertrophic cardiomyopathy: a systematic review and meta-analysis

Background

A subcutaneous implantable cardioverter-defibrillator (S-ICD) is an alternative to a transvenous implantable cardio defibrillator (TV-ICD). An S-ICD reduces the risk of transvenous lead placement. However, further research is required to determine how S-ICDs affect patients with hypertrophic cardiomyopathy (HCM). In this study, we investigated the comparative efficacy and safety of S-ICDs versus TV-ICDs in HCM.

Methods

On December 6th, 2023, we performed a comprehensive search of the PubMed, Embase, Scopus, and Cochrane databases to identify randomized clinical trials (RCTs) and observational studies comparing S-ICDs with TV-ICDs in HCM patients published from 2004 until 2023. No language restrictions were applied. The primary outcome was appropriate shocks (AS), with inappropriate shocks (IAS), and device-related complications considered as secondary outcomes. Odds ratios (ORs) and 95% confidence intervals (CIs) were pooled using a random effects model. The ROBINS-I tool was used to assess the risk of bias of the studies.

Results

The search yielded 1,114 records. Seven studies comprising 4,347 HCM patients were included, of whom 3,325 (76.0%) had TV-ICDs, and 1,022 (22.6%) had S-ICDs. There were 2,564 males (58.9%). The age range was from 39.1 to 49.4 years. Compared with the TV-ICD group, the S-ICD cohort had a significantly lower incidence of device-related complications (OR 0.52; 95% CI: 0.30-0.89; P=0.02; I2=4%). Contrastingly, there were no statistically significant differences in the occurrences of AS (OR 0.49; 95% CI: 0.22-1.08; P=0.08; I2=75%) and IAS (OR 1.03; 95% CI: 0.57-1.84; P=0.93; I2=65%) between the two device modalities. In the analysis of the overall risk of bias in the studies, we found 42% of them with several, 28% with moderate, and 14% with low risk of bias.

Conclusions

In HCM patients, S-ICDs were associated with a lower incidence of device-associated problems than TV-ICDs. AS and IAS incidence rates were similar between groups. These findings may assist clinicians in determining the most suitable device for treating patients with HCM.

The Subcutaneous ICD: A Review of the UNTOUCHED and PRAETORIAN Trials

The ICD is an important part of the treatment and prevention of sudden cardiac death in many high-risk populations. Traditional transvenous ICDs (TV-ICDs) are associated with certain short- and long- term risks. The subcutaneous ICD (S-ICD) was developed in order to avoid these risks and complications. However, this system is associated with its own set of limitations and complications. First, patient selection is important, as S-ICDs do not provide pacing therapy currently. Second, pre-procedural screening is important to minimise T wave and myopotential oversensing. Finally, until recently, the S-ICD was primarily used in younger patients with fewer co-morbidities and less structural heart disease, limiting the general applicability of the device. S-ICDs achieve excellent rates of arrhythmia conversion and have demonstrated noninferiority to TV-ICDs in terms of complication rates in real-world studies. The objective of this review is to discuss the latest literature, including the UNTOUCHED and PRAETORIAN trials, and to address the risk of inappropriate shocks.

The subcutaneous implantable cardioverter-defibrillator: Current trends in clinical practice between guidelines and technology progress

The subcutaneous implantable cardioverter defibrillator (S-ICD) is a valuable alternative to the conventional trans-venous ICD (TV-ICD) for the prevention of sudden cardiac death (SCD). Prospective registries showed that the S-ICD is safe and effective in treating ventricular tachyarrhythmias in high-risk patients without pacing indications. While in earlier studies patients implanted with S-ICDs were young and mostly affected by channelopathies, contemporary S-ICD cohorts include patients with severely impaired left ventricular function and significant comorbidities. This review focuses on S-ICD evidence-based use and highlights current gaps between guidelines recommendations and real-world clinical practice.

Entirely subcutaneous defibrillator and complex congenital heart disease: Data on long-term clinical follow-up

AIM

To describe the long-term follow-up of patients with complex congenital heart disease who underwent subcutaneous implantable cardiac defibrillator (S-ICD), focusing on local complications, appropriate and inappropriate shocks.

METHODS

Patients with complex congenital heart disease underwent S-ICD implant in two centers with the conventional technique. Data at follow-up were retrieved from clinical notes and institutional database.

RESULTS

Eight patients were implanted in two centres between 2010 and 2016. Median age at implant was 37.5 years (range 13-57). All patients who were deemed suitable for S-ICD implant passed the pre-procedural screening. Three patients were previously implanted with a anti-bradycardia device, one of whom with CRT. In one patient the device was explanted due to local infection. During the total median follow-up of 874 d, one patient had an appropriate and one inappropriate shock triggered by fast atrial tachycardia. None of the patients had inappropriate shocks secondary to T wave oversensing or electrical interference with anti- bradycardia devices.

CONCLUSION

S-ICD appears to be effective and safe in patients with complex congenital heart disease.

Sudden cardiac death: New approaches for implantable cardioverter-defibrillators (ICDs)

The implantable cardioverter-defibrillator (ICD) has shown its superiority to anti-arrhythmic drugs in the prevention of sudden cardiac death. However, the conventional transvenous ICDs are still associated with substantial risks and comorbidities mainly related to the transvenous leads. The recent advent of an entirely sub-cutaneous ICD (S-ICD) represents an important progress in the defibrillation technology towards a less invasive approach. Clinical data are growing regarding the safety and efficacy of S-ICD in prevention of sudden cardiac death in selected patients without pacing indications. This novel technology seems promising and particularly beneficial in young patients with channelopathies, conditions at high risk of infection, or in those who experienced previous complications related to the transvenous leads. The S-ICD technology is still developing regarding the device, diagnostic capabilities, and the surgical implantation technique. Further advancements and potential integration with the leadless pacing technology may realize an outstanding evolution in defibrillation therapy and prevention of sudden cardiac death in the near future.

Established and novel treatment options in acute myocarditis, with or without heart failure

Acute myocarditis is a disorder characterized by an unpredictable clinical course which ranges from asymptomatic, incidentally discovered forms, to cases with fulminant course and adverse outcome. The most challenging issues in the context of acute myocarditis are the appearance of difficult to treat heart failure in the acute phase and the potential progression in the long-term to dilated cardiomyopathy. Areas covered: With respect to available treatment options in acute myocarditis, in the absence of specific guidelines, management is supportive and overall empirical, especially for the oligo- or asymptomatic patients with preserved ejection fraction. Haemodynamically instable patients should be treated in referral centers with capability of advanced cardiopulmonary support. Patients with heart failure but without haemodynamic impairment should be treated according to the heart failure guidelines. Endomyocardial biopsy may be performed in an individualized basis both for diagnostic purposes and to guide treatment, based on the detection or not of viral genome. Expert commentary: Apart from the already established treatments, novel therapies against several targets are currently investigated and are expected to contribute to a more efficacious management options in the future. Increased awareness among medical professionals is essential for the early diagnosis and best care of acute myocarditis patients.