Subcutaneous implantable cardioverter-defibrillators: Function, indications and implantation

Therapy with subcutaneous implantable cardioverter-defibrillators (S-ICD) without intravascular or intracardiac placement of leads may be an alternative to conventional ICD therapy in selected patients. If preoperative screening reveals the potential usefulness of a S-ICD system, the surgical procedure itself is relatively easy to perform and takes about the same time as conventional single chamber ICD systems. Ideal indications are primary prophylaxis, for example in patients after myocardial infarction with persistent impaired left ventricular (LV) function and also primary and secondary prophylaxis in patients with diseases known to generate ventricular fibrillation (e.g. long QT syndrome and Brugada syndrome). The success of S‑ICD therapy depends on careful planning and performance of the implantation of the system anatomically adapted to the individual patient. Another advantage of the S‑ICD besides the renunciation of transvenous leads is the maintenance of the integrity of shoulder musculature and fascia preserving unlimited activity of the pectoral girdle. The S‑ICD therapy is nowadays not applicable for the treatment of ventricular tachycardia, as the S‑ICD (in contrast to the conventional system) does not provide ventricular overstimulation. Furthermore, aside from a short period of postshock pacing, the S‑ICD does not comprise properties for permanent pacing; therefore, pacemaker-dependent patients are not eligible for S‑ICD therapy. Currently, the combination of leadless pacing with S‑ICD is under investigation to overcome most of the current limitations of S‑ICD therapy. © 2016, Springer-Verlag Berlin Heidelberg.