Complications associated with defibrillation threshold testing: The Canadian experience David Birnie, MD,* Stanley Tung, MD, † Christopher Simpson, MD, ‡ Eugene Crystal, MD, § Derek Exner, MD,  Felix-Alejandro Ayala Paredes, MD, ¶ Andrew Krahn, MD, # Ratika Parkash, MD,** Yaariv Khaykin, MD, †† Francois Philippon, MD, ‡‡ Peter Guerra, MD, §§ Shane Kimber, MD, " Douglas Cameron, MD, ¶¶ Jeffrey S. Healey, MD ## From the *University of Ottawa Heart Institute, Ottawa, Ontario, † St. Paul’s Hospital Vancouver, British Columbia, ‡ Queen’s University, Kingston General Hospital, Kingston, Ontario, § Sunnybrook Health Sciences Centre, Toronto, Ontario,  Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, ¶ Centre Hospital University de Sherbrooke-Hop Fleurimont, Sherbrooke, Quebec, # London Health Sciences Centre, London, Ontario, **Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, †† Southlake Regional Health Centre, Newmarket, Ontario, ‡‡ Laval Hospital Ste-Foy, Quebec, §§ Montreal Heart Institute, Montreal, Quebec, " University of Alberta, Edmonton, Alberta, ¶¶ Toronto General Hospital, University Health Network, Toronto, Ontario, and ## Hamilton Health Sciences Center, Hamilton, Ontario, Canada. BACKGROUND Defibrillation threshold (DFT) testing has tradi- tionally been a routine part of implantable cardioverter-defibril- lator (ICD) implantation, despite a lack of compelling evidence that it predicts or improves outcomes. In the past, when devices were much less reliable, DFT testing seemed prudent; however, modern ICD systems have such a high rate of successful defibril- lation that many electrophysiologists now question whether DFT testing is still worthwhile, particularly since DFT testing may now be the highest acute risk component of ICD implantation. OBJECTIVE The purpose of this study was to systematically docu- ment complications directly attributable to intraoperative DFT test- ing. METHODS We obtained data on DFT-related complications from all 21 adult ICD implant centers in Canada, covering the period from January 1, 2000, to September 30, 2006. RESULTS There were a total of 19,067 ICD implants in Canada during the study period. There were three DFT testing–related deaths, five DFT testing–related strokes, and 27 episodes that required prolonged resuscitation. Two patients had significant clinical sequelae after prolonged resuscitation. CONCLUSIONS The risk of severe complications from intraopera- tive DFT testing appears small, even allowing for the underesti- mation of its true rate with the current study methodology. These slight but measurable risks must be considered when assessing the risk-benefit ratio of the procedure. Additional data from ongoing prospective ICD registries and/or clinical trials are required. KEYWORDS Implantable cardioverter-defibrillators (ICDs): compli- cations; Defibrillation threshold testing; Risks: stroke (Heart Rhythm 2008;5:387–390) © 2008 Heart Rhythm Society. All rights reserved. Intraoperative defibrillation testing is usually performed during the insertion of implantable cardioverter-defibrilla- tors (ICDs). 1,2 Defibrillation threshold (DFT) testing at the time of ICD implantation was developed in the early days of the ICD when devices were less reliable. Early ICDs, in- serted via thoracotomy, often had high DFTs, despite all attempts at optimization. However, over the last 20 years, many features of the ICD have evolved such as transvenous placement, active “can,” dual-coil leads, biphasic wave- forms, programmable polarity, and rapid charge times that have greatly improved the efficacy of defibrillation. 3 The Dr. C. Simpson, Dr. F. Philippon Dr. D. Birnie, Dr. A. Krahn, and Dr. J. Healey have received research grants/support from Boston Scientific. Dr. D. Birnie, Dr. F. Philippon, Dr. D. Exner, and Dr. C. Simpson have received research grants/support from Medtronic. Dr. D. Exner and Dr. F Philippon have received research grants/support from St. Jude. Dr. D. Exner has received research grants/support from GE Healthcare, and Dr. C. Simpson has received research grants/support from Sorin Group. Dr. D. Exner, Dr. C. Simpson, Dr. R. Parkash, and Dr. F. Philippon have received honoraria from Medtronic. Dr. D. Exner and Dr. R. Parkash have received honoraria from St. Jude. Dr. D. Exner has received honoraria from GE Healthcare, and Dr. C. Simpson has received honoraria from Boston Scientific. Dr. D. Exner, Dr. D. Birnie, Dr. S. Kimber, and Dr. F. Philippon have received speakers’ fees from Medtronic. Dr. S. Kimber has received speakers’ fees from St. Jude and Guidant. Dr. D. Exner and Dr. F. Philippon have received speakers’ fees from GE Healthcare and St. Jude. Dr. F. Ayala- Paredes has received speakers’ fees from Biotronic. Dr. D. Exner has served as a consultant for Medtronic and GE Healthcare. Dr. F. Ayala-Paredes has served as a consultant for Biotronic, and Dr. F. Philippon has served as a consultant for Boston Scientific. The remaining authors report no conflicts. Address reprint requests and correspondence: Dr. D. Birnie, University of Ottawa Heart Institute, 40 Ruskin Road, Ottawa ON, K1Y 4W7, Can- ada. E-mail address: dbirnie@ottawaheart.ca. (Received September 1, 2007; accepted November 19, 2007.) 1547-5271/$ -see front matter © 2008 Heart Rhythm Society. All rights reserved. doi:10.1016/j.hrthm.2007.11.018