Decline of defibrillation testing in the clinical practice: an 8-year nation-wide assessment

Defibrillation testing (DT), which consists of inducing and terminating ventricular fibrillation during implantable cardioverter-defibrillator (ICD) implantation, is considered a standard procedure and has been performed in all ICD trials. Moreover, it is part of the manufacturers' instructions approved by regulatory authorities. Nevertheless, its clinical usefulness has not been proven and no recommendation is given by international guidelines. In the meantime, concerns have been raised about the balance between possible DT-related risks and long-term benefits, and data from ‘real-world’ experience show that a number of first implantation procedures are performed without any induction test. In a 2005 national population survey involving 229 (67%) out of 343 Italian implanting centres,1 DT was not performed in 2356 (30%) of the 7857 de novo ICD implantations. In 35 (15%) centres, the induction test was performed in <25% of patients, whereas in 136 (59%) centres, it was performed in >75% of patients. Owing to the large number of centres involved, this survey contributed to stirring up the already existing debate on this issue among many implanting physicians in Italy and raised awareness in many of them that DT could be omitted in some patients. Subsequently, we carried out a prospective observational study (the Safety of Two Strategies of ICD Management at Implantation, SAFE-ICD study)2 to evaluate the outcome of two strategies: performing vs. not performing DT. Patients were consecutively enrolled in a sample of 41 Italian centres from April 2008 to May 2009, and the decision to perform DT was left to the physicians' discretion. Unexpectedly, 61% of patients did not undergo DT in the study. The study demonstrated similar extremely low rates of severe complications on ICD implantation and of sudden cardiac death or resuscitation over 2-year follow-up in both groups, thus indicating the limited clinical relevance of DT and supporting a strategy of omitting DT during ICD implantation. The above results were consistent with those found during the same years by a multicentre network of 111 Italian centres3 in which DT was not performed in 678 (67%) of 2082 implantations. To assess the current Italian clinical practice of DT, we repeated the survey by collecting data on ICD implantation procedures performed from January to June 2013 in 276 centres in Italy. Defibrillation testing was not performed in 5163 (72%) of the 7135 de novo ICD implantations. In 200 (72%) centres, the induction test was performed in <25% of patients, whereas in 63 (23%), it was performed in >75% of patients. Similar results emerged when only the 202 centres that participated in both the 2005 and the 2013 surveys were included in the analysis: DT was not performed in 4153 (72%) of the 5760 de novo ICD implantations, and in 143 (71%) centres. Defibrillation testing was performed in <25% of patients. The main reasons for continuing to perform DT reported by physicians who participated in the 2013 survey were: secondary prevention, inherited arrhythmogenic diseases and can positioned on the right thoracic site. Comparison between the 2005 and 2013 surveys (Figure 1) shows that the practice of DT has significantly changed over 8 years in Italy and is profoundly different from that adopted in other countries. For example, in a European Heart Rhythm Association survey assessing the practice of DT in 57 European centers, only 19% of centres did not perform DT in 2010,4 and in the largest American National Cardiovascular Data ICD Registry, DT was not performed in only 29% of 64 227 initial ICD implantation procedures performed at 1,261 facilities in 2010.5 Left panel. Cumulative results of percent patients who performed DT in 2005 and 2013 in Italy. Right panel. Defibrillation testing distribution of centres (subdivided in quartiles) according to the percentage of patients who performed intraoperative DT. DT means defibrillation testing. There is an ongoing debate as to the need for conducting intraoperative DT at the time of ICD implantation. Although the SAFE-ICD study and a recent meta-analysis6 supported the paradigm shift towards elimination of DTs at initial implants, in the era of evidence-based medicine only randomized trials are equipped to provide sufficiently strong evidence to change the standards of clinical practice. Hopefully, new evidence on arrhythmic death and shock efficacy will be provided by the Shockless Implant Evaluation, (SIMPLE) trial, which randomly compared DT with no-DT implantations and has recently been presented. Although the study was not powered to evaluate mortality as a primary endpoint, the trial demonstrated non-inferiority for the primary end-point of ineffective clinical shock or arrhythmic death (7.2% in the no-DT group versus 8.3% in the DT group). The expectations are that the results, by confirming the results of SAFE-ICD, will help the scientific community to draw up international recommendations and manufacturers to obtain regulatory approval for the revision of their information for the use of ICDs. In the meantime, our data show that most electrophysiologists, in Italy more than elsewhere, have spontaneously modified their clinical practice, even in the absence of scientific evidence or clear recommendations. We believe that the above nation-wide studies have contributed to their decisions. Conflict of interest: F. Accardi and S Valsecchi are employees of Boston Scientific, Milano. No other authors disclose any relationship with industry and financial associations from within the past 2 years that might pose a conflict of interest in connection with the submitted article. This work was supported by a grant from Boston Scientific.