[The subcutaneous cardioverter-defibrillator: When less is more]

Comparative Assessment of Transvenous versus Subcutaneous Implantable Cardioverter-defibrillator Therapy Outcomes: An Updated Systematic Review and Meta-analysis

BACKGROUND

Subcutaneous (S-ICD) and transvenous (TV-ICD) implantable cardioverter-defibrillator devices effectively reduce the incidence of sudden cardiac death in patients at a high risk of ventricular arrhythmias. This study aimed to evaluate the safe replacement of TV-ICD with S-ICD based on updated recent evidence.

METHODS

We systematically searched EMBASE, JSTOR, PubMed/MEDLINE, and Cochrane Library on 30 July 2021 following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

We identified 26 studies that examined 7542 (58.27%) patients with S-ICD and 5400 (41.72%) with TV-ICD. The findings indicated that, compared to patients with TV-ICD, patients with S-ICD had a lower incidence of defibrillation lead failure (odds ratio [OR], 0.12; 95% confidence interval [CI], 0.01-0.98; p = 0.05), lead displacement or fracture (OR, 0.25; 95% CI, 0.12-0.86; p = 0.0003), pneumothorax and/or hemothorax (OR: 0.22, 95% CI 0.05, 0.97, p = 0.05), device failure (OR: 0.70, 95% CI 0.51, 0.95, p = 0.02), all-cause mortality (OR: 0.44 [95% CI 0.32, 0.60], p < 0.001), and lead erosion (OR: 0.01, 95% CI 0.00, 0.05, p < 0.001). Patients with TV-ICD had a higher incidence of pocket complications than patients with S-ICD (OR, 2.13; 95% CI, 1.23-3.69; p = 0.007) and a higher but insignificant incidence of inappropriate sensing (OR, 3.53; 95% CI, 0.97-12.86; p = 0.06).

CONCLUSIONS

The S-ICD algorithm was safer and more effective than the TV-ICD system as it minimized the incidence of pocket complications, lead displacement or fracture, inappropriate sensing, defibrillation lead failure, pneumothorax/hemothorax, device failure, lead erosion, and all-cause mortality. Future studies should explore the scope of integrating novel algorithms with the current S-ICD systems to improve cardiovascular outcomes.

[A life-saving shock from a subcutaneous ICD during skydiving]

We report the case of a 38-year-old man who was implanted a subcutaneous implantable cardioverter-defibrillator (S-ICD) and then performed a skydive from a height of 3000 m. During the jump, he lost consciousness due to ventricular fibrillation (VF). The S‑ICD detected the VF properly and successfully shocked the arrhythmia. Our illustrative case emphasizes the S‑ICD as an appropriate therapy in patient with life-threatening arrhythmias even under extreme conditions.

Heart Failure With Reduced Ejection Fraction And A Narrow QRS Complex: Combination Of A Subcutaneous Defibrillator With Cardiac Contractility Modulation

Cardiac contractility modulation (CCM) is a relatively new electrical therapy for heart failure patients with reduced ejection fraction. The majority of patients eligible for CCM will also need an implantable cardioverter-defibrillator (ICD). To-date, three pacing electrodes are mandatory for CCM therapy because the current CCM signal delivery algorithm requires sequential intracardiac sensing of a p-wave, followed by appropriately timed ventricular activation by the two ventricular septal leads. As there is no device combining CCM with ICD functions, most CCM patients will need multiple intracardiac electrodes, which increase the cumulative risk for complications such as systemic infections, thrombosis of central venous lines, insulation failures or lead fractures. The long-term complications associated with trans-venous ICD leads have led to the development of a totally subcutaneous implantable cardioverter-defibrillator (S-ICD). In this essay the two technologies CCM and S-ICD are reviewed. Additionally, we present their successful combination on the basis of a case report on the first patient receiving both devices.