A Randomised Trial of S-ICD Implantation With and Without Defibrillation Testing

Implantable Cardioverter Defibrillator (ICD) implant improves survival in patients with a higher risk for sudden cardiac death. There are 2 types of ICD available; transvenous ICD (TV-ICD) and subcutaneous ICD (S-ICD). During ICD implant, defibrillation testing (DFT) is performed to test functionality of the device. However, DFT can be associated with complications such as inability to convert, complications arising from general anaesthesia, prolonged resuscitation, stroke and death. Whereas DFT may be associated with complications, the benefit of DFT is debated as literature shows there is only a modest average effect of DFT, if any, on mortality, shock efficacy or safety. Recently it was shown in a randomized controlled trial called 'SIMPLE' that routine defibrillation testing of TV-ICDs at the time of implant does not improve shock efficacy or reduce arrhythmic death. For S-ICD there is only limited data available of the effect of DFT on S-ICD efficacy. Data have however shown that the conversion efficacy of the S-ICD is comparable to TV-ICD. DFT is currently performed in standard S-ICD implants, but is omitted in specific cases. However, an alternative method to evaluate the correct position may be desired when omitting DFT. The PRAETORIAN Score is developed using computer modelling data on factors influencing defibrillation thresholds. The PRAETORIAN score represents the chance of a patient having an elevated defibrillation threshold and consequently failing a DFT or conversion of a spontaneous arrhythmia episode. The score was retrospectively validated in two studies with 180 and 321 patients. It was reported that most S-ICD implants are performed under general anesthesia, however other anesthesia protocols are used as well. One of the most predominant factors to use general anesthesia is the performance of the DFT. If this is omitted, other anesthesia protocols may be a good option for many patients as well.