title: Circadian pattern of ventricular tachyarrhythmias in patients with implantable cardioverter-defibrillators.
abstract: OBJECTIVE
  This study examined the temporal patterns of ventricular tachycardia detections by implantable cardioverter-defibrillators for circadian variability.
  
  
  BACKGROUND
  Previous studies of circadian arrhythmia patterns have been methodologically limited by very brief observational periods. Late-generation implantable cardioverter-defibrillators accurately record the times of arrhythmia detections during unlimited follow-up.
  
  
  METHODS
  Forty-three patients with late-generation implantable cardioverter-defibrillators were followed up for 226 +/- 179 days (mean +/- SD). The times of all recorded episodes of ventricular tachyarrhythmias were retrieved from the data log of each device during follow-up.
  
  
  RESULTS
  The weighted distribution of 830 ventricular tachyarrhythmia episodes from the 43 patients fit a single harmonic sine curve model with a peak between 2 and 3 P.M. (95% confidence interval 1:13 to 4:13 P.M., R = 0.75, p < 0.05). The distributions of spontaneously terminating episodes, episodes receiving device therapy, episodes receiving shocks and episodes in the absence of antiarrhythmic therapy also fit the sine curve model (all R = 0.53 and 0.73, all p < 0.05), all with peak frequencies between 2:08 and 3:09 P.M. and 95% confidence intervals for peak frequencies between 11:38 A.M. and 5:07 P.M. Episodes recorded during continuous antiarrhythmic drug therapy did not fit the model (p > 0.05).
  
  
  CONCLUSIONS
  The distribution of ventricular tachyarrhythmias detected by late-generation implantable cardioverter-defibrillators follows a circadian pattern, with a peak tachycardia frequency between noon and 5 P.M. This pattern was not observed in patients receiving antiarrhythmic drug therapy. Knowledge of circadian periodicity for these events has implications for patient management.
authors.affiliation: Department of Medicine, Medical College of Virginia, Richmond 23298.
authors.forename: M A
authors.initials: MA
authors.lastname: Wood
authors.forename: P M
authors.initials: PM
authors.lastname: Simpson
authors.forename: W B
authors.initials: WB
authors.lastname: London
authors.forename: B S
authors.initials: BS
authors.lastname: Stambler
authors.forename: J M
authors.initials: JM
authors.lastname: Herre
authors.forename: R C
authors.initials: RC
authors.lastname: Bernstein
authors.forename: K A
authors.initials: KA
authors.lastname: Ellenbogen
mesh_terms: D000368:Aged; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D002940:Circadian Rhythm; D017147:Defibrillators, Implantable; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017180:Tachycardia, Ventricular / Q000188:drug therapy / Q000503:physiopathology* / Q000628:therapy
chemical_list: D000889:Anti-Arrhythmia Agents