title: Heart rate variability in white-coat hypertension.
abstract: OBJECTIVE
  The objective of this study was to compare heart rate variability (HRV) in patients with essential hypertension, in patients with white-coat hypertension and in normotensive control individuals, and to investigate a possible relation between HRV and vasoactive hormones.
  
  
  METHODS
  Patients with essential hypertension (n=19, 61 years, median and interquartile range: 40-66 years), patients with white-coat hypertension (n=8, 52 years, median and interquartile range: 41-64 years) and normotensive participants (n=13, 50 years, median and interquartile range: 39-57 years) participated in the study. HRV was measured at rest in the supine position, during standing and during controlled forced breathing (respiration frequency >20/min). Power spectral density was calculated using Fourier transformation.
  
  
  RESULTS
  Controlled breathing caused a decrease in low frequency (LF) variation and LF/high frequency variation (LF/HF) in all blood pressure groups. The decrease in LF was smaller in the hypertensive group (-60 ms2) than in the normotensive group (-139 ms2) (P=0.03; hypertensive group vs. normotensive group). The decrease in LF/HF induced by controlled breathing was -0.9 ms in the hypertensive group, -2.0 ms2 in the white-coat hypertensive group and -2.8 ms2 in the normotensive group, (P=0.037; hypertensive group vs. normotensive group). We found a positive correlation between baseline plasma renin concentration and LF (r=0.330, P=0.037) and LF/HF (r=0.378, P=0.016) at rest.
  
  
  CONCLUSIONS
  The observed differences in HRV might reflect the impaired responsiveness to autonomic challenge in hypertensive patients. We did not find the HRV spectrum in white-coat hypertension different from the HRV spectrum in hypertension or normotension.
authors.affiliation: Department of Medical Research, Holstebro Hospital and Aarhus University, Aarhus, Denmark. libma@ringamt.dk
authors.forename: Line B
authors.initials: LB
authors.lastname: Madsen
authors.forename: Jens K
authors.initials: JK
authors.lastname: Rasmussen
authors.forename: Dorthe S
authors.initials: DS
authors.lastname: Møller
authors.forename: Ole
authors.initials: O
authors.lastname: Nyvad
authors.forename: Erling B
authors.initials: EB
authors.lastname: Pedersen
mesh_terms: D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000097:blood; D000809:Angiotensins / Q000097:blood; D001127:Arginine Vasopressin / Q000097:blood; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D001945:Breathing Exercises; D016022:Case-Control Studies; D016232:Endothelins / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood; D010817:Physician-Patient Relations; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology*
chemical_list: D000809:Angiotensins; D016232:Endothelins; D001127:Arginine Vasopressin; D020097:Natriuretic Peptide, Brain; D000450:Aldosterone; D012083:Renin