ICDS
High defibrillation energy requirements are encountered rarely with modern dual-chamber implantable cardioverter-defibrillator systems
1 Utah Heart Clinic Arrhythmia Services, LDS Hospital, 324 10th Avenue, Suite 206, Salt Lake City, UT 84103, USA; 2 University of Iowa Hospitals, Iowa City, IA, USA; 3 North Ohio Research, Ltd, Elyria, OH, USA; 4 The Integra Group, Brooklyn Park, MN, USA; 5 Boston Scientific CRM, St Paul, MN, USA
Aims: Defibrillation conversion testing to assure a 10 J safety margin is a standard practice during implantable cardioverter-defibrillator (ICD) implantation. Little data are available on the number of patients who do not have a 10 J margin initially and therefore require system revisions, further testing, or a higher energy output device.
Methods and results: The INTRINSIC RV study enrolled 1530 new ICD recipients who were not in permanent atrial fibrillation who received a VITALITY AVT (Guidant, St Paul, MN, USA) standard energy (31 J maximum) ICD and underwent defibrillation conversion testing at the time of implantation from 108 centres. Among enrolled patients, 59 (3.9%) did not initially meet the 10 J safety margin criterion. In these 59 patients, a 10 J safety margin was achieved by making at least one system revision: reversing shocking polarity (n = 33, 56%), right ventricular lead repositioning (n = 19, 32%), repeat testing at a later date (n = 1, 2%), adding a subcutaneous array (n = 1, 2%), or other means (n = 10, 17%). Only New York Heart Association class (P = 0.001) and no previous myocardial infarction (P = 0.044) predicted a failed initial conversion test. There were no reported complications from ICD shock testing.
Conclusion: Successful defibrillation conversion criteria with the first configuration tested with a standard energy device is almost always met with modern dual-chamber ICD systems. The need for revising the initial ICD shock configuration to achieve a 10 J safety margin appears extremely low and of low risk.
Key Words: Implantable cardioverter-defibrillator, Defibrillation energy requirements, Ventricular fibrillation
* Corresponding author: Intermountain Medical Center, Eccles Outpatient Care Center, 5169 Cottonwood Street, Suite 510, Murray, UT 84157, USA. Tel: +1 801 408 3900; fax: +1 801 408 3909; E-mail address: john.day{at}cv-research.org
This study is registered with www.clinicaltrials.gov (identifier nct00148967
[ClinicalTrials.gov]
). This manuscript was presented in part at the Heart Rhythm Society Annual Scientific Sessions, May 2005, New Orleans, LA, USA.
Manuscript submitted 4 November 2007. Accepted after revision 14 January 2008.