title: Indications for internal cardioverter defibrillator implantation predict time to first shock and the modulating effect of beta-blockers.
abstract: BACKGROUND
  Patients receive implantable cardioverter defibrillator (ICD) for varying indications. Whether these indications influence the time to first ICD shock is suspected but not confirmed. The modulating effect of beta-blockers on shock-free survival is not fully elucidated.
  
  
  METHODS
  A retrospective analysis of 230 consecutive patients (age 63 +/- 14 years, 79% men, 75% ischemic, 70% beta-blockers) implanted with an ICD was performed. Patients were divided into 4 groups depending on the ICD indication: groups A (secondary prevention of sudden death), B (left ventricular ejection fraction < or = 35% and positive electrophysiology study [EPS]), C (left ventricular ejection fraction < or = 35% and negative EPS or no EPS performed), and D (patients who did not meet inclusion criteria for groups A, B, or C). Time to shock was analyzed by the Kaplan-Meier method.
  
  
  RESULTS
  During a mean follow-up of 489 +/- 280 days, 57 (24.7%) patients received 82 shocks (49% appropriate). The 1-year shock-free survival for patients in groups A, B, C, and D were 57%, 77%, 79%, and 91%, respectively (P = .03), for total shocks and 75%, 92%, 92%, and 100%, respectively (P = .007), for appropriate shocks. For patients in group A, the use of beta-blockers increased the 1-year shock-free survival from 48% to 61% for total shocks and from 65% to 79% for appropriate shocks.
  
  
  CONCLUSIONS
  Time to first shock is determined by the indication for ICD implantation and is not predicted by the results of EPS. Patients with secondary indications for ICD implantation are at highest risk of shocks and may deserve consideration for prophylactic antiarrhythmic drugs. beta-Blockers increase the time to first ICD shock in patients implanted for secondary prevention of sudden death.
authors.affiliation: University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Haitham
authors.initials: H
authors.lastname: Hreybe
authors.forename: Maninder
authors.initials: M
authors.lastname: Bedi
authors.forename: Rana
authors.initials: R
authors.lastname: Ezzeddine
authors.forename: William
authors.initials: W
authors.lastname: Barrington
authors.forename: Sandeep
authors.initials: S
authors.lastname: Jain
authors.forename: Ogundu
authors.initials: O
authors.lastname: Ngwu
authors.forename: Samir
authors.initials: S
authors.lastname: Saba
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D001145:Arrhythmias, Cardiac / Q000517:prevention & control* / Q000628:therapy; D017147:Defibrillators, Implantable; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D000319:Adrenergic beta-Antagonists