Subcutaneous ICD combined with VT ablation for the secondary prevention of sudden cardiac death: pilot data from the prospective multinational SICD-VTAbl study

Background The aim of the Subcutaneous ICD Combined with Ventricular Tachycardia Ablation (SICD-VTAbl) Study is to provide preliminary data on the safety and efficacy of a management strategy that incorporates S-ICD implantation and VT ablation among patients with a secondary prevention indication for an ICD. We hypothesize that VT ablation for the prevention of monomorphic VT recurrence combined with S-ICD implantation for termination of life-threatening VT/VF is safe, while reducing the need for device interventions and systemic complications associated with conventional transvenous ICD implantation for secondary prevention. Methods SICD-VTAbl is an uncontrolled, prospective, multinational observational study, conducted in France, Germany, US (Rochester NY, and Rochester MN) and coordinated in Israel. We aim to prospectively enroll 30 patients presenting with scar-related VT/VF who will undergo VT ablation/substrate modification followed by S-ICD implantation. The primary endpoint is the first occurrence of S-ICD therapy (appropriate and inappropriate). Secondary endpoints include separate occurrence of appropriate and inappropriate ICD therapies, peri-procedural complications, and adverse clinical outcomes. Results We provide clinical, arrhythmia, and outcome data on the first 15 patients enrolled in the SICD-VTAbl Study through February 2021. Mean age was 59±12 years, 78% were males, 60% had New York Heart Association (NYHA) Class ≥II symptoms, 20% had renal insufficiency, and 33% were treated with an antiarrhythmic medication (all amiodarone). Periprocedural, arrhythmia, and long-term outcome data are provided in Table 1. There were no major complications associated with the VT ablation and the S-ICD implantation procedures. During a median follow-up of 6 months (interquartile range: 2–12 months), 2 patients (13%) received S-ICD therapy: one patient (7%) experienced VF terminated by the S-ICD and one patient experienced a single episode of inappropriate S-ICD therapy. Adverse events during follow-up, unrelated to study procedures, occurred in 3 patients (20%): hospitalization for heart failure exacerbation (N=1) and non-cardiovascular hospitalizations (N=2). None of the patients died during follow-up (Table 1). Conclusions Our preliminary data from the SICD-VTAbl Study suggest that a management approach that incorporates VT ablation followed by S-ICD implantation is safe and may lead to improved arrhythmia and clinical outcomes in patients presenting with a secondary prevention indication for an ICD. FUNDunding Acknowledgement Type of funding sources: Other. Main funding source(s): Research grant to Sheba Medical Center from Boston Scientific

Comparative Effectiveness of Implantable Defibrillators for Asymptomatic Brugada Syndrome: A Decision‐Analytic Model

Background Optimal management of asymptomatic Brugada syndrome (BrS) with spontaneous type I electrocardiographic pattern is uncertain. Methods and Results We developed an individual‐level simulation comprising 2 000 000 average‐risk individuals with asymptomatic BrS and spontaneous type I electrocardiographic pattern. We compared (1) observation, (2) electrophysiologic study (EPS)‐guided implantable cardioverter‐defibrillator (ICD), and (3) upfront ICD, each using either subcutaneous or transvenous ICD, resulting in 6 strategies tested. The primary outcome was quality‐adjusted life years (QALYs), with cardiac deaths (arrest or procedural‐related) as a secondary outcome. We varied BrS diagnosis age and underlying arrest rate. We assessed cost‐effectiveness at $100 000/QALY. Compared with observation, EPS‐guided subcutaneous ICD resulted in 0.35 QALY gain/individual and 4130 cardiac deaths avoided/100 000 individuals, and EPS‐guided transvenous ICD resulted in 0.26 QALY gain and 3390 cardiac deaths avoided. Compared with observation, upfront ICD reduced cardiac deaths by a greater margin (subcutaneous ICD, 8950; transvenous ICD, 6050), but only subcutaneous ICD improved QALYs (subcutaneous ICD, 0.25 QALY gain; transvenous ICD, 0.01 QALY loss), and complications were higher. ICD‐based strategies were more effective at younger ages and higher arrest rates (eg, using subcutaneous devices, upfront ICD was the most effective strategy at ages 20–39.4 years and arrest rates >1.37%/year; EPS‐guided ICD was the most effective strategy at ages 39.5–51.3 years and arrest rates 0.47%–1.37%/year, and observation was the most effective strategy at ages >51.3 years and arrest rates <0.47%/year). EPS‐guided subcutaneous ICD was cost‐effective ($80 508/QALY). Conclusions Device‐based approaches (with or without EPS risk stratification) can be more effective than observation among selected patients with asymptomatic BrS. BrS management should be tailored to patient characteristics.

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.

Subcutaneous Implantable Cardioverter Defibrillator (S-ICD) Electrode Fracture: Follow-up, Troubleshooting and Evaluation

Introduction: The subcutaneous-ICD (S-ICD) and its electrode were developed to avoid long-term complications of transvenous leads in the vasculature. Methods: We report a case of unexpected, inappropriate S-ICD shocks due to oversensing of high amplitude, non-physiologic, electrical noise artifacts that were not preceded by high impedance alerts or sensing electrogram noise detections. Results: Following explant, high-magnification, X-ray imaging of the S-ICD electrode demonstrated partial fracture of the distal sensing conductor located near a short radius bend in the electrode at the electrode-header interface. Conclusions: Clinicians should be aware of a potential for fatigue failure fracture of the S-ICD electrode. Recommendations for systematic S-ICD follow-up and troubleshooting are discussed.