title: Unexpected deviation in circadian variation of ventricular arrhythmias: the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial).
abstract: OBJECTIVE
  This study sought to determine whether circadian patterns in ventricular arrhythmias (VAs) occur in a current primary prevention defibrillator (implantable cardioverter-defibrillator [ICD]) population.
  
  
  BACKGROUND
  Cardiovascular events, including VAs, demonstrate biorhythmic periodicity.
  
  
  METHODS
  We tested for deviation from the previously described occurrences of a morning peak, early morning nadir, and peak on Mondays in ICD therapies using generalized estimating equations and Student t tests. All hypothesis tests were performed in the entire cohort of patients with VAs as well as pre-specified subgroups.
  
  
  RESULTS
  Of 811 patients with an ICD, 186 subjects experienced 714 ICD therapy episodes for life-threatening VA. There was no morning (6 am to 12 pm) peak in therapies for the entire cohort or any subgroups. The overall cohort and several subgroups had a typical early morning (12 am to 6 am) nadir in therapies, with significantly less than 25% of therapies occurring during this 6-h block (all p < 0.05). A significant peak in therapies on Mondays occurred only in patients not on beta-blocker therapy (22% of events for the week, p = 0.029).
  
  
  CONCLUSIONS
  In the SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) population, the distribution of life-threatening VA failed to show a typical early morning peak or increased VA events on Mondays. A typical early morning nadir was seen in the entire cohort. An increased rate of events on Mondays was found in the subgroup of subjects not on beta-blocker therapy. These findings may indicate suppression of the neurohormonal triggers for VA by current heart failure therapy, particularly the use of beta-blockers in heart failure.
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington.
authors.forename: Kristen K
authors.initials: KK
authors.lastname: Patton
authors.affiliation: Duke Clinical Research Institute, Durham, North Carolina.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Hellkamp
authors.affiliation: Duke Clinical Research Institute, Durham, North Carolina.
authors.forename: Kerry L
authors.initials: KL
authors.lastname: Lee
authors.affiliation: Duke Clinical Research Institute, Durham, North Carolina.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Mark
authors.affiliation: Seattle Institute for Cardiac Research, Seattle, Washington.
authors.forename: George W
authors.initials: GW
authors.lastname: Johnson
authors.affiliation: Seattle Institute for Cardiac Research, Seattle, Washington.
authors.forename: Jill
authors.initials: J
authors.lastname: Anderson
authors.affiliation: Seattle Institute for Cardiac Research, Seattle, Washington.
authors.forename: Gust H
authors.initials: GH
authors.lastname: Bardy
authors.affiliation: Department of Medicine, University of Washington, Seattle, Washington. Electronic address: jpoole@u.washington.edu.
authors.forename: Jeanne E
authors.initials: JE
authors.lastname: Poole
mesh_terms: D000368:Aged; D002940:Circadian Rhythm / Q000502:physiology*; D015331:Cohort Studies; D016757:Death, Sudden, Cardiac / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control*; D017147:Defibrillators, Implantable / Q000639:trends; D006333:Heart Failure / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D017180:Tachycardia, Ventricular / Q000401:mortality / Q000503:physiopathology* / Q000628:therapy*; D016896:Treatment Outcome
keywords: circadian; implantable cardioverter-defibrillator; septadian; ventricular arrhythmia
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