title: Risk Factors for Inadequate Defibrillation Safety Margins Vary With the Underlying Cardiac Disease: Implications for Selective Testing Strategies.
abstract: In view of the shift from routine toward no or selective defibrillation testing, optimization of the current risk stratification for inadequate defibrillation safety margins (DSMs) could improve individualized testing decisions. Given the pathophysiological differences in myocardial substrate between ischemic and nonischemic heart disease (IHD/non-IHD) and the accompanying differences in clinical characteristics, we studied inadequate DSMs and their predictors in relation to the underlying etiology.
  
  
  
  Cohort of routine defibrillation tests (n = 785) after first implantable cardioverter defibrillator (ICD)-implantations at the Radboud UMC (2005-2014). A defibrillation threshold >25 J was regarded as an inadequate DSM. In total, 4.3% of patients had an inadequate DSM; in IHD 2.5% versus 7.3% in non-IHD (P = 0.002). We identified a group of non-IHD patients at high risk (13-42% inadequate DSM); the remainder of the cohort (>70%) had a risk of only 2% (C-statistic entire cohort 0.74; C-statistic non-IHD 0.82). This was based upon two identified interaction terms: (1) non-IHD and age (aOR 0.94 [95% CI 0.91-0.97]); (2) non-IHD and the indexed left ventricular (LV) internal diastolic diameter (aOR 3.50 [95% CI 2.10-5.82]).
  
  
  
  The present study on risk stratification for an inadequate DSM not only confirms the importance of making a distinction between IHD and non-IHD, but also shows that risk factors in an entire cohort (LV dilatation, age) may only apply to a subgroup (non-IHD). Appreciation of this concept could favorably affect current risk stratification. If confirmed, our approach may be used to optimize individualized testing decisions in an upcoming era of non-routine testing.
authors.affiliation: Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Judith L
authors.initials: JL
authors.lastname: Bonnes
authors.affiliation: Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Sjoerd W
authors.initials: SW
authors.lastname: Westra
authors.affiliation: Department of Cardiology, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Leon H R
authors.initials: LH
authors.lastname: Bouwels
authors.affiliation: Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Menko Jan
authors.initials: MJ
authors.lastname: DE Boer
authors.affiliation: Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Brouwer
authors.affiliation: Department of Cardiology, Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Joep L R M
authors.initials: JL
authors.lastname: Smeets
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D016009:Chi-Square Distribution; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000009:adverse effects / Q000295:instrumentation*; D004869:Equipment Safety; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000150:complications; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D009426:Netherlands; D016017:Odds Ratio; D061214:Patient Safety; D011474:Prosthesis Design; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome
keywords: cardiomyopathy; defibrillation; defibrillation threshold testing; implantable cardioverter defibrillator; myocardial infarction; risk stratification