title: Changes in heart rate and heart rate variability before ambulatory ischemic events(1).
abstract: OBJECTIVE
  The aim of this study was to determine the time course of autonomic nervous system activity preceding ambulatory ischemic events.
  
  
  BACKGROUND
  Vagal withdrawal can produce myocardial ischemia and may be involved in the genesis of ambulatory ischemic events. We analyzed trajectories of heart rate variability (HRV) 1 h before and after ischemic events, and we examined the role of exercise and mental stress in preischemic autonomic changes.
  
  
  METHODS
  Male patients with stable coronary artery disease (n = 19; 62.1 +/- 9.3 years) underwent 48-h ambulatory electrocardiographic monitoring. Frequency domain HRV measures were assessed for 60 min before and after each of 68 ischemic events and during nonischemic heart rate-matched control periods.
  
  
  RESULTS
  High-frequency HRV decreased from -60, -20 to -10 min before ischemic events (4.8 +/- 1.3; 4.6 +/- 1.3; 4.4 +/- 1.2 ln [ms(2)], respectively; p = 0.04) and further from -4, -2 min, until ischemia (4.4 +/- 1.3; 4.1 +/- 1.3; 3.7 +/- 1.2 ln [ms(2)]; p's < 0.01). Low frequency HRV decreases started at -4 min (p < 0.05). Ischemic events occurring at high mental activities were preceded by depressed high frequency HRV levels compared with events at low mental activity (p = 0.038 at -4 min, p = 0.045 at -2 min), whereas the effects of mental activities were not observed during nonischemic control periods. Heart rate variability measures remained significantly decreased for 20 min after recovery of ST-segment depression when events were triggered by high activity levels.
  
  
  CONCLUSIONS
  Autonomic changes consistent with vagal withdrawal can act as a precipitating factor for daily life ischemia, particularly in episodes triggered by mental activities.
authors.affiliation: Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences Bethesda, Bethesda, Maryland 20814, USA. wjkop@mxb.usuhs.mil
authors.forename: W J
authors.initials: WJ
authors.lastname: Kop
authors.forename: R J
authors.initials: RJ
authors.lastname: Verdino
authors.forename: J S
authors.initials: JS
authors.lastname: Gottdiener
authors.forename: S T
authors.initials: ST
authors.lastname: O'Leary
authors.forename: C N
authors.initials: CN
authors.lastname: Bairey Merz
authors.forename: D S
authors.initials: DS
authors.lastname: Krantz
mesh_terms: D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D015444:Exercise / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000503:physiopathology*; D013315:Stress, Psychological / Q000503:physiopathology