The Italian subcutaneous implantable cardioverter-defibrillator survey: S-ICD, why not?

Implantable cardioverter-defibrillators (ICDs) are an established therapy for the prevention of sudden cardiac death (SCD).1 Conventional ICDs rely on transvenous leads to deliver defibrillation shocks [transvenous-ICD (T-ICD)] and, if necessary, to provide cardiac pacing. Implantable cardioverter-defibrillator therapy is not free from procedural complications; these are mainly associated with the insertion of transvenous leads, e.g. pneumothorax, cardiac tamponade, and vascular damage.2 Moreover, the long-term risks of devicerelated complications are of great concern, especially in view of the improved survival of ICD recipients.3 In order to avoid the risks involved in accessing the heart via the vascular system and to overcome recurring problems with transvenous leads, a subcutaneous ICD (S-ICD) has recently been developed in which the electrode systemis placed entirely subcutaneously, outside the chest. The available data suggest that S-ICDs are effective in terminating life-threatening ventricular arrhythmias (VAs).4-6 Consequently, a Class IIa recommendation for S-ICD has been added to the most recent European Society of Cardiology (ESC) Guidelines for patients with VAs.1 However, S-ICDs are not suitable for patients who require pacing for bradycardia or cardiac resynchronization therapy (CRT), nor for thosewho suffer from VAs that can easily be terminated by antitachycardia pacing (ATP). The Italian survey 'S-ICDWhy Not' was an independent initiative taken by the Italian Heart Rhythm Society (Associazione Italiana Aritmologia e Cardiostimolazione-AIAC). The primary aim of this survey was to provide information, including clinical characteristics, selection criteria, and factors guiding the choice of ICD type, in a representative sample of consecutive patients who underwent ICD implantation in Italian clinical practice. Data were analysed to measure the actual suitability for S-ICD and to evaluate the adoption of this novel therapy. Methods Study design All Italian centres with experience in S-ICD implantation were invited to participate. Centres were asked to enrol consecutive patients at the time of de novo implantation of a new single- or dual-chamber T-ICD or an S-ICD, in a 3 month row, between 1 September 2015 and 31 December 2015. At the time of implantation, all patients provided written informed consent for data storage and analysis. Data were collected by means of online internet entry. An electronic case report form was created to capture demographics and clinical characteristics, selection criteriaassessed prior to implantation, and factors guiding the choice of ICD type. The contents of the form are detailed in Appendix. All centres were also asked to report the total number of implantation procedures performed during the observation period, i.e. de novo, replacement and upgrade implantations of single-or dual-chamber T-ICD, ICD for CRT (CRT-D), and S-ICD. Secondary prevention of SCD was defined as the ICD implantation in patients with documented ventricular fibrillation, haemodynamically not tolerated or recurrent sustained ventricular tachycardia in the absence of reversible causes.1 The prevalence of conditions for a recommendation for pacing according to ESC Guidelines8 was measured to quantify the actual need for permanent pacing.