Demonstration of circadian rhythm in heart rate turbulence using novel application of correlator functions

Heart Rhythm. 2007 Mar;4(3):292-300. doi: 10.1016/j.hrthm.2006.11.016. Epub 2006 Nov 18.


Background: Demonstration of a circadian rhythm in two parameters of heart rate turbulence--turbulence onset (TO) and turbulence slope (TS)--has been difficult.

Objective: The aim of this study was to devise a new method for detecting circadian rhythm in noisy data and to apply it to selected Holter recordings from two postmyocardial infarction databases: Cardiac Arrhythmia Suppression Trial (CAST, n = 684) and Innovative Stratification of Arrhythmic Risk (ISAR, n = 327).

Methods: For each patient, TS and TO were calculated for each hour with >4 ventricular premature contractions (VPCs). An autocorrelation function Corr(Deltat) = <TS(t) TS(t + Deltat)> then was calculated and averaged over all patients. Positive Corr(Deltat) indicates that TS at a given hour and Deltat hours later are similar. TO was treated likewise. Simulations and mathematical analysis showed that a circadian rhythm required Corr(Deltat) to have a U-shape consisting of positive values near Deltat = 0 and 23 and negative values for intermediate Deltat. Significant deviation of Corr(Deltat) from the correlator function of pure noise was evaluated as a Chi-square value.

Results: Circadian patterns were not apparent in hourly averages of TS and TO plotted against clock time, which had large error bars. However, their correlator functions produced Chi-square values of approximately 10 in CAST (both P <.0001) and approximately 3 in ISAR (both P <.0001), indicating the presence of circadian rhythmicity.

Conclusion: Correlator functions may be a powerful tool for detecting the presence of circadian rhythms in noisy data, even with recordings limited to 24 hours.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Antagonists / therapeutic use
  • Chi-Square Distribution
  • Circadian Rhythm* / drug effects
  • Databases, Factual
  • Electrocardiography, Ambulatory
  • Female
  • Heart Conduction System / drug effects
  • Heart Conduction System / physiopathology
  • Heart Rate* / drug effects
  • Humans
  • Male
  • Mathematical Computing
  • Middle Aged
  • Myocardial Infarction / drug therapy
  • Myocardial Infarction / physiopathology
  • Predictive Value of Tests
  • Signal Processing, Computer-Assisted
  • Ventricular Premature Complexes / physiopathology


  • Adrenergic beta-Antagonists