title: Is there increased sympathetic activity in patients with hypertrophic cardiomyopathy?
abstract: OBJECTIVE
  This study aimed to assess autonomic nervous system activity in patients with hypertrophic cardiomyopathy.
  
  
  BACKGROUND
  Patients with hypertrophic cardiomyopathy are traditionally thought to have increased sympathetic activity. However, convincing evidence is lacking.
  
  
  METHODS
  Heart rate variability was assessed from 24-h ambulatory electrocardiographic (Holter) recordings in 31 patients with hypertrophic cardiomyopathy and 31 age- and gender-matched normal control subjects in a drug-free state. Spectral heart rate variability was calculated as total (0.01 to 1.00 Hz), low (0.04 to 0.15 Hz) and high (0.15 to 0.40 Hz) frequency components using fast Fourier transformation analysis.
  
  
  RESULTS
  There was a nonsignificant decrease in the total frequency component of heart rate variability in patients with hypertrophic cardiomyopathy compared with that of normal subjects (mean +/- SD 7.24 +/- 0.88 versus 7.59 +/- 0.57 ln[ms2], p = 0.072). Although there was no significant difference in the high frequency component (5.31 +/- 1.14 versus 5.40 +/- 0.91 ln[ms2], p = 0.730), the low frequency component was significantly lower in patients than in normal subjects (6.25 +/- 1.00 versus 6.72 +/- 0.61 ln[ms2], p = 0.026). After normalization (i.e., division by the total frequency component values), the low frequency component was significantly decreased (38 +/- 8% versus 43 +/- 8%, p = 0.018) and the high frequency component significantly increased (16 +/- 6% versus 12 +/- 6%, p = 0.030) in patients with hypertrophic cardiomyopathy. The low/high frequency component ratio was significantly lower in these patients (0.94 +/- 0.64 versus 1.33 +/- 0.55, p = 0.013). In patients with hypertrophic cardiomyopathy, heart rate variability was significantly related to left ventricular end-systolic dimension and left atrial dimension but not to maximal left ventricular wall thickness. No significant difference in heart rate variability was found between 14 victims of sudden cardiac death and 10 age- and gender-matched low risk patients.
  
  
  CONCLUSIONS
  Our observations suggest that during normal daily activities, patients with hypertrophic cardiomyopathy experience a significant autonomic alteration with decreased sympathetic tone.
authors.affiliation: Department of Cardiological Sciences, St. George's Hospital Medical School, London, England, United Kingdom.
authors.forename: L
authors.initials: L
authors.lastname: Fei
authors.forename: A K
authors.initials: AK
authors.lastname: Slade
authors.forename: K
authors.initials: K
authors.lastname: Prasad
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: D000293:Adolescent; D000328:Adult; D000638:Amiodarone / Q000627:therapeutic use; D002312:Cardiomyopathy, Hypertrophic / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D016022:Case-Control Studies; D002940:Circadian Rhythm; D016757:Death, Sudden, Cardiac / Q000209:etiology; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D000638:Amiodarone