title: Differences in outcomes between patients treated with single- versus dual-chamber implantable cardioverter defibrillators: a substudy of the Multicenter Automatic Defibrillator Implantation Trial II.
abstract: OBJECTIVE
  We sought to evaluate the influence of single- versus dual-chamber implantable cardioverter defibrillators (ICDs) on the occurrence of heart failure and mortality as well as appropriate and inappropriate ICD therapy in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II).
  
  
  BACKGROUND
  In MADIT-II, ICD therapy in patients with a prior myocardial infarction and ejection fraction < or =0.30 was associated with a 31% reduction in risk of mortality when compared to conventionally treated patients. An unexpected finding was an increased occurrence of hospitalization for heart failure in the ICD group.
  
  
  METHODS
  Data from 717 patients randomized to ICD therapy with single- or dual-chamber pacing devices in MADIT-II were retrospectively analyzed. Endpoints selected for analysis included death from any cause, new or worsening heart failure requiring hospitalization, death or heart failure, appropriate therapy for ventricular tachycardia (VT) or ventricular fibrillation (VF), and inappropriate ICD therapy for atrial fibrillation or supraventricular tachycardia.
  
  
  RESULTS
  A total of 404 single-chamber ICDs (S-ICDs) and 313 dual-chamber ICDs (D-ICDs) were implanted. Patients receiving D-ICDs were at a higher risk at baseline than those receiving S-ICDs, with older age, higher NYHA class, more frequent prior CABG, wider QRS complex, more LBBB, higher BUN level, a history of more atrial arrhythmias requiring treatment, and a longer time interval from their index myocardial infarction to enrollment. While there was a trend toward an increase in adverse outcomes in the D-ICD group, no statistically significant differences in heart failure or mortality were observed between S-ICD versus D-ICD groups.
  
  
  CONCLUSIONS
  Patients with D-ICDs had a nonsignificant trend toward higher mortality and heart failure rates than patients with S-ICDs.
authors.affiliation: Mid-America Cardiology and the Department of Internal Medicine, Division of Cardiology, University of Kansas Hospital, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA. ldberenbom@mac.md
authors.forename: Loren D
authors.initials: LD
authors.lastname: Berenbom
authors.forename: Brian C
authors.initials: BC
authors.lastname: Weiford
authors.forename: James L
authors.initials: JL
authors.lastname: Vacek
authors.forename: Martin P
authors.initials: MP
authors.lastname: Emert
authors.forename: W Jackson
authors.initials: WJ
authors.lastname: Hall
authors.forename: Mark L
authors.initials: ML
authors.lastname: Andrews
authors.forename: Scott
authors.initials: S
authors.lastname: McNitt
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zareba
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Moss
mesh_terms: D001145:Arrhythmias, Cardiac / Q000401:mortality* / Q000628:therapy*; D015897:Comorbidity; D017147:Defibrillators, Implantable / Q000145:classification / Q000706:statistics & numerical data*; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000401:mortality* / Q000628:therapy*; D011379:Prognosis; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D016019:Survival Analysis; D015996:Survival Rate; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology