title: Sympathetic activity, assessed by power spectral analysis of heart rate variability, in white-coat, masked and sustained hypertension versus true normotension.
abstract: OBJECTIVE
  To assess, in a population-based approach, sympathetic nervous system activity by the use of power spectral analysis of heart rate variability, in normotension, white-coat hypertension, masked hypertension and sustained hypertension.
  
  
  METHODS
  The electrocardiographic RR interval was registered in the supine and standing positions and the low-frequency and high-frequency components of its variability were quantified. Cut-off values of 140/90 mmHg for conventional blood pressure and 135/85 mmHg for daytime ambulatory blood pressure were used to define the four blood pressure groups.
  
  
  RESULTS
  After exclusion of patients with diabetes, myocardial infarction or treated hypertension, 1485 subjects with complete data remained for the analysis in the supine position. Age averaged 39 +/- 14 years; 54% were women. Conventional and ambulatory blood pressure averaged, respectively, 122 +/- 16/79 +/- 11 mmHg and 124 +/- 12/77 +/- 8 mmHg. After adjusting for demographic, anthropometric and lifestyle characteristics, the low-frequency to high-frequency ratio (geometric mean) averaged 0.81 in normotension and was significantly higher in white-coat hypertension (1.11; P < 0.001), based on a higher low-frequency component and a lower high-frequency component (P < 0.01). This ratio was not significantly different between normotension, masked hypertension (0.97) and sustained hypertension (0.93). The adjusted standing-to-supine ratio of the high-frequency component (geometric mean) was significantly higher in sustained hypertension (0.50) than in normotension (0.39; P < 0.01), but not in white-coat (0.40) and masked hypertension (0.45).
  
  
  CONCLUSIONS
  The findings at rest are compatible with increased sympathetic activity and decreased parasympathetic modulation in white-coat hypertension, with normal autonomic cardiac regulation in masked and sustained hypertension. In addition, sustained hypertension is characterized by a blunted decrease of the high-frequency component on standing.
authors.affiliation: Hypertension and Cardiovascular Rehabilitation Unit, University of Leuven K.U. Leuven, Leuven, Belgium. robert.fagard@uz.kuleuven.ac.be
authors.forename: Robert H
authors.initials: RH
authors.lastname: Fagard
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Stolarz
authors.forename: Tatiana
authors.initials: T
authors.lastname: Kuznetsova
authors.forename: Jitka
authors.initials: J
authors.lastname: Seidlerova
authors.forename: Valérie
authors.initials: V
authors.lastname: Tikhonoff
authors.forename: Tomasz
authors.initials: T
authors.lastname: Grodzicki
authors.forename: Yuri
authors.initials: Y
authors.lastname: Nikitin
authors.forename: Jan
authors.initials: J
authors.lastname: Filipovsky
authors.forename: Jan
authors.initials: J
authors.lastname: Peleska
authors.forename: Edoardo
authors.initials: E
authors.lastname: Casiglia
authors.forename: Lutgarde
authors.initials: L
authors.lastname: Thijs
authors.forename: Jan A
authors.initials: JA
authors.lastname: Staessen
authors.forename: Kalina
authors.initials: K
authors.lastname: Kawecka-Jaszcz
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016683:Supine Position; D013564:Sympathetic Nervous System / Q000503:physiopathology*