title: Decreased heart rate variability in patients with congestive heart failure and chronotropic incompetence.
abstract: Heart rate variability was studied in 41 patients (aged 48 +/- 12 years) with congestive heart failure secondary to idiopathic dilated cardiomyopathy. All patients underwent a treadmill exercise test and 24-hour Holter ECG monitoring. Chronotropic incompetence was defined as the failure to achieve > or = 80% of the predicted maximal heart rate response given by 220--age (years) at peak exercise. Spectral heart rate variability was analyzed from 24-hour Holter ECGs and was expressed as total (0.01-1.00 Hz), low (0.04-0.15 Hz), and high (0.15-0.40 Hz) frequency components. The standard deviation of all normal RR intervals (SDNN) was also computed. Chronotropic incompetence was observed in ten patients. Peak oxygen consumption was significantly lower in patients with chronotropic incompetence compared with those without chronotropic incompetence. The total (5.11 +/- 1.26 ln [ms2] vs 6.41 +/- 0.92 ln [ms2]; P = 0.009) and low (3.38 +/- 1.65 ln [ms2] vs 5.45 +/- 1.34 ln [ms2]; P = 0.003), but not the high (3.42 +/- 1.04 ln [ms2] vs 4.00 +/- 1.12 ln [ms2]; P = 0.249) frequency components of heart rate variability were significantly lower in patients with chronotropic incompetence, although there was no significant difference in mean heart rate (88 +/- 20 beats/min vs 86 +/- 15 beats/min; P = 0.831) or left ventricular ejection fraction (22% +/- 10% vs 24% +/- 10%; P = 0.619). SDNN was also significantly lower in patients with chronotropic incompetence compared with those without chronotropic incompetence (64 +/- 34 ms vs 102 +/- 37 ms; P = 0.030).
  
  
  CONCLUSIONS
  The observation that heart rate variability is significantly decreased in patients with congestive heart failure who have chronotropic incompetence suggests that chronotropic incompetence may relate to an abnormal autonomic influence on the heart in these patients.
authors.affiliation: Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Fei
authors.forename: P J
authors.initials: PJ
authors.lastname: Keeling
authors.forename: N
authors.initials: N
authors.lastname: Sadoul
authors.forename: X
authors.initials: X
authors.lastname: Copie
authors.forename: M
authors.initials: M
authors.lastname: Malik
authors.forename: W J
authors.initials: WJ
authors.lastname: McKenna
authors.forename: A J
authors.initials: AJ
authors.lastname: Camm
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology*; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000503:physiopathology*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology; D015716:Electrocardiography, Ambulatory; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006321:Heart / Q000294:innervation; D006333:Heart Failure / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009200:Myocardial Contraction / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D012815:Signal Processing, Computer-Assisted