[Journey of the S‑ICD to first-line therapy]

The subcutaneous implantable cardioverter-defibrillator (S-ICD®, Boston Scientific, Marlborough, MA, USA, previously Cameron Health, San Clemente, CA, USA) represents an important milestone in ICD therapy for prevention of sudden cardiac death (SCD). Since the introduction of the S‑ICD in 2010, the device has undergone further development. Based on the unique feature of an entirely extracardiac implantation, the S‑ICD is able to reduce the common perioperative and long-term complications of the usual endovascular implanted ICD systems. Especially for patients with a complex anatomy and no option of an endovascular lead implantation, the S‑ICD offers a potential alternative. Regarding the initial uncertainty if this innovative ICD approach is actually reliable in detecting and terminating ventricular arrhythmias has been resolved by multiple clinical studies and trials providing evidence for an effective treatment. Based on the obvious advantages compared to conventional ICD systems, the question arises if the S‑ICD should actually be the first choice in the majority of all primary prevention patients in the future. Furthermore, recent data from large registries show that S‑ICD indications are also expanding in secondary prevention patients. As a consequence the S‑ICD was listed in the 2015 ESC guidelines as an alternative therapeutic option with a class IIa recommendation in patients with an ICD indication not requiring pacing for bradycardia, cardiac resynchronization therapy or anti-tachycardia pacing (ATP). In addition, the American Heart Association guidelines refer to class I recommendation for patients with a complex anatomy and venous access problems or at a high risk for infections who need ICD therapy. Limitations with respect to the not available pacing option of S‑ICD might be also overcome by a potential combination with a leadless pacemaker in the near future. This article provides an overview of recent developments of the S‑ICD and reviews the most recent literature and ongoing studies.