Automatic implantable defibrillators: an update for emergency physicians

Implantable cardioverter defibrillators (ICDs) are first-line therapeutic devices for preventing sudden death due to ventricular arrythmia. The antitachycardia pacing of ICDs terminates a large proportion of arrhthymias painlessly. Energy consumption is low, avoiding shocks from the device. The implanted leads required by conventional ICDs have been associated with a high rate of complications related to the implantation process and to vascular injury, pneumothorax, perforations, and more. Long-term complications related to malfunctioning leads or infection at the implant site can oblige removal. Subcutaneous ICDs (S-ICDs), developed to minimize complications caused by endovascular leads, have been used in Spain since 2013 and in other parts of Europe since 2009. S-ICDs detect and treat arrhythmias with shocks that are always greater than those delivered by transvenous ICDs; moreover, S-ICDs cannot provide antitachycardia pacing. So far, S-ICDs have proven highly effective and safe, producing a very low rate of inappropriate shocks thanks to the various improvements in software and programing. They are larger than transvenous ICDs, however, and their batteries are shorter lived because they deliver much higher-energy shocks. S-ICDs also lack the ability to provide antibradycardia pacing. A new defibrillation system has been developed in recent years in an attempt to overcome the disadvantages of S-ICDs while retaining their advantages. The shock generators of the new extravascular implantable devices (EV-ICDs) are the same size as those of transvenous ICDs and theoretically have the same life span. They are implanted inside the left lateral chest wall, and a defibrillation and pacing lead is placed in the retrosternal space, covering the craniocaudal axis of the cardiac silhouette. This system offers low-energy cardiac defibrillation and is able to provide both antitachycardia and antibradycardia pacing. Because the potential complications of using these novel devices may generate emergency department visits, we must become familiar with them, given that treatment is not exclusively the remit of cardiologists and experts in arrhythmias but of all physicians who manage cardiovascular emergencies.