BACKGROUNDThe subcutaneous implantable cardioverter-defibrillator (ICD) was designed to avoid complications related to the transvenous ICD lead by using an entirely extrathoracic placement. Evidence comparing these systems has been based primarily on observational studies. METHODSWe conducted a noninferiority trial in which patients with an indication for an ICD but no indication for pacing were assigned to receive a subcutaneous ICD or transvenous ICD. The primary end point was the composite of device-related complications and inappropriate shocks; the noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio (subcutaneous ICD vs. transvenous ICD) was 1.45. A superiority analysis was prespecified if noninferiority was established. Secondary end points included death and appropriate shocks. RESULTSA total of 849 patients (426 in the subcutaneous ICD group and 423 in the transvenous ICD group) were included in the analyses. At a median follow-up of 49.1 months, a primary end-point event occurred in 68 patients in the subcutaneous ICD group and in 68 patients in the transvenous ICD group (48-month Kaplan-Meier estimated cumulative incidence, 15.1% and 15.7%, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.71 to 1.39; P = 0.01 for noninferiority; P = 0.95 for superiority). Device-related complications occurred in 31 patients in the subcutaneous ICD group and in 44 in the transvenous ICD group (hazard ratio, 0.69; 95% CI, 0.44 to 1.09); inappropriate shocks occurred in 41 and 29 patients, respectively (hazard ratio, 1.43; 95% CI, 0.89 to 2.30). Death occurred in 83 patients in the subcutaneous ICD group and in 68 in the transvenous ICD group (hazard ratio, 1.23; 95% CI, 0.89 to 1.70); appropriate shocks occurred in 83 and 57 patients, respectively (hazard ratio, 1.52; 95% CI, 1.08 to 2.12). CONCLUSIONSIn patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to devicerelated complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.

In patients with repaired TOF, biventricular dysfunction on CMR imaging was associated with major adverse clinical outcomes. The quantified thresholds (RV EF <30% and LV EF <45%) may be implemented in noninvasive risk stratification.

Aims To guarantee uninterrupted function of the subcutaneous implantable cardioverter-defibrillator (S-ICD), the pulse generator needs to be surgically replaced before the battery is depleted. The risks related to this replacement substantially impact long-term outcome for S-ICD recipients, as the majority will undergo one or several of these procedures in their lifetime. We aim to describe the procedural characteristics of the replacement procedure and to provide an insight in the complications associated with these replacements. Methods and results In this retrospective analysis, data from replacement procedures and follow-up visits were collected from all patients who underwent elective S-ICD generator replacement in our tertiary centre from June 2014 until November 2019. Original device position was assessed using the PRAETORIAN score. Complications were defined as those requiring surgical intervention, systemic antibiotic treatment, or device extraction. Seventy-two patients were included, with a median follow-up of 1.9 years (IQR 0.6–3.3 years) after replacement. Battery depletion occurred after 5.9 ± 0.7 years. The pulse generator was repositioned in patients with a PRAETORIAN score ≥90 to minimize the defibrillation threshold. Although there was an increase in impedance compared to the implant procedure, first shock conversion rate during defibrillation testing was 91.4% with a success rate of 100% after multiple attempts. Two patients developed a complication after, respectively, 9 and 21 months, resulting in a complication rate of 1.4% per year. Conclusion With a median follow-up of 1.9 years, this study shows a low complication rate after S-ICD replacement, with a first shock conversion rate of 91.4%.

Background Inherited channelopathies, cardiomyopathies and structural heart diseases are known to increase the risk of sudden cardiac death in children and are occasionally treated with an implantable cardioverter-defibrillator (ICD). Due to their physical growth and higher level of activity, children experience more adverse events than adults, such as lead fractures, vascular problems and infections. The subcutaneous ICD (S-ICD) was introduced to avoid these lead-related complications and is expected to be especially beneficial for children who require ICD therapy. However, long-term follow-up data of this population are lacking. Purpose To evaluate long-term clinical outcomes of the S-ICD in the paediatric population. Methods Follow-up data were prospectively collected of all paediatric patients (age &lt;18 years) who received their S-ICD in our tertiary centre between November 2009 and June 2019. Clinical outcomes that were assessed were appropriate or inappropriate shocks and complications that required surgical intervention. Results A total of 21 paediatric patients received an S-ICD, with a median age of 15 years (ranged 8–17) and a median body mass index of 18.8 kg/m2 (ranged 15.5–28.8, lowest weight 30kg). The indication for ICD implantation was mostly idiopathic ventricular fibrillation (38.1%) or genetic arrhythmic disease (28.6%). The subcutaneous lead was implanted in an S-shape to accommodate for growth in small patients, and straightening of the lead could be observed on successive chest X-rays (see figure). There was no need for lead or device revisions in this cohort. After a median follow-up of 4.3 years (IQR 2.7–6.5), five patients (23.8%) received an appropriate shock for ventricular arrhythmias and six patients (28.6%) received an inappropriate shock for supraventricular tachycardia (n=4) or double-counting (n=2). Complications that required device extraction occurred in three patients after 0.8±1.1 years and was the result of inappropriate shocks (n=1) and pocket infection (n=2). In two patients the S-ICD was extracted due to progression of their cardiac disease, of whom one needed biventricular pacing and one underwent heart transplantation. Conclusions The S-ICD appears efficacious in this heterogeneous paediatric population. Although higher than reported in adults, the long-term complication rate in paediatric S-ICD recipients is similar to the paediatric transvenous ICD population. Funding Acknowledgement Type of funding source: None