title: Heart rate variability in hypertension caused by sleep disordered breathing and its modification by CPAP.
abstract: OBJECTIVE
  1) To analyze heart rate variability (HRV) changes, reflecting the sympathovagal balance with secondary hypertension caused by sleep disordered breathing (SDB), compared to healthy controls and essential hypertension without SDB; 2) to compare HRV changes between various degrees of SDB severity; and 3) to test the modification of HRV indices by continuous positive airway pressure (CPAP) in SDB patients.
  
  
  BACKGROUND
  Differentiation of secondary hypertension caused by SDB from essential hypertension and healthy controls by ambulatory blood pressure measurement (ABPM) and its modification by CPAP, requires an analysis of HRV changes, as frequently used for the prediction of cardiovascular risk.
  
  
  METHODS
  HRV changes were analyzed in 48 adults divided into six groups according to the apnoea/hypopnoea index (AHI), i.e. three groups with various degrees of SDB, a group with severe SDB after CPAP application, a group with essential hypertension without SDB, and a group of healthy controls. Night-time and daytime values of low frequency (LF) and high frequency (HF) bands and the LF/HF ratio were compared in the six groups.
  
  
  RESULTS
  The night-time values of LF bands were higher in severe than in moderate and mild degrees of SDB, and the correlation of LF/HF ratio with AHI (r = 0.3511) suggests the gradual increase of sympathetic predominance with the severity of SDB. The high sympathetic activity substantially decreased after application of CPAP in severe SDB.
  
  
  CONCLUSIONS
  The increased nocturnal values of the LF band and the LF/HF ratio, caused by frequent apnoea/ hypopnoea episodes, support the usefulness of HRV spectral analysis for the prediction of cardiovascular risk in patients with SDB (Tab. 1, Fig. 3, Ref. 36).
authors: Department of Physiology, Faculty of Medicine, University of PJ Safarik, Kosice, Slovakia.
authors: S
authors: S
authors: Gresova
authors: Z
authors: Z
authors: Tomori
authors: J
authors: J
authors: Widdicombe
authors: V
authors: V
authors: Donic
authors: M
authors: M
authors: Kundrik
authors: I
authors: I
authors: Bacova
authors: M
authors: M
authors: Pallayova
mesh_terms: D045422:Continuous Positive Airway Pressure; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000150:complications* / Q000503:physiopathology; D008875:Middle Aged; D017286:Polysomnography; D012891:Sleep Apnea Syndromes / Q000150:complications / Q000503:physiopathology / Q000628:therapy*