Is Defibrillation Testing Necessary for Implantable Transvenous Defibrillators?

Abstract

Because the implantable cardioverter defibrillator (ICD) was introduced into clinical practice, insertion of these devices has typically involved defibrillation testing (DT). However, DT has never been shown to independently improve patient outcomes. The rationale for DT has always been that the induction of ventricular fibrillation (VF) immediately after ICD insertion allows the implanting team to verify that the ICD can appropriately sense VF and deliver a high-energy shock that can effectively terminate this arrhythmia.1 The first ICD systems were complex, using epicardial patches and monophasic shock waveforms, thus accurate sensing and termination of VF were frequently in question. However, the ICD evolved over time, with the introduction of transvenous systems, biphasic waveforms, and active cans, which made failure to sense and treat VF much less common.2,3 Modern ICDs are also capable of delivering energies >40 J, thus many have started to question the rationale for DT in the modern era.4–7 Response by Russo et al on p 351 During the past 10 years, there has been a dramatic shift in practice, such that DT is performed in <50% of ICD implants in some jurisdictions. This change was not driven by the results of randomized trials, but by changing opinions of clinicians,4 based on the following insights from observational studies: (1) intraoperative DT is usually successful and clinicians do not always act on unfavorable results; (2) intraoperative DT is an unproven surrogate for clinical shock efficacy; (3) the likelihood of a failed appropriate clinical shock is low and does not appear lower among patients who have DT; and (4) DT is associated with uncommon, but serious complications and adds cost and complexity to the ICD implant procedure. A large randomized evaluation of DT will soon be completed8; however, the observational data …