Is defibrillation testing necessary for implantable transvenous defibrillators?: defibrillation testing is necessary at the time of implantable cardioverter defibrillator implantation.

Abstract

Clinical trials have documented the efficacy of implantable cardioverter-defibrillators (ICDs) for the primary and secondary prevention of sudden cardiac death.1–7 These trials have typically involved induction of ventricular fibrillation (VF) at the time of implantation to demonstrate effective arrhythmia termination. In fact, defibrillation testing (DT) was also performed at the time of implantation of ICDs in those patients whose data were used to seek approval of the US Federal Drug Administration for general use, and instructions for usage include labeling with DT. This is also the case for the recently approved subcutaneous ICD. Response by Healey et al on p 346 Higher defibrillation thresholds (DFTs) were seen with older ICDs implanted using an epicardial approach, abdominal pulse generators, or monophasic waveforms. In contrast, modern technology now includes devices with biphasic waveform shocks and pectoral active can systems that result in more effective defibrillation.8–11 In addition, devices now have higher output, routinely delivering ≥35 J and also increasing the chance of effective defibrillation. Therefore, it has been suggested that these new defibrillation technologies may eliminate the need for DT. Although the risk of failing defibrillation is now much lower, patients receiving ICDs today may have more comorbidities, more severe heart failure, and a higher risk of failing shocks. If a high defibrillation energy requirement is identified at the time of initial implantation, system revision is typically performed with the intent of increasing the likelihood that the ICD will effectively terminate ventricular tachycardia (VT) or VF when it occurs spontaneously. So, we need to ask ourselves, why would a physician implant this potentially life-saving device without testing? The term DFT refers to the minimum shock strength that defibrillates.12 Historically, a threshold below a specific value has been used as an acceptable criterion for device implantation. …