title: Effect of hormone replacement therapy on cardiac autonomic modulation.
abstract: OBJECTIVE
  To investigate the effects of hormone replacement therapy (HRT) on heart rate variability (HRV) in healthy postmenopausal women.
  
  
  METHODS
  Two groups were evaluated: group 1 (G1): 20 women not undergoing HRT (60 ± 5.89 years), group 2 (G2): 20 women undergoing HRT (59 ± 5.70 years). The HRTs involved were either conjugated equine estrogen with or without medroxyprogesterone, synthetic estrogen hormone, estradiol associated with norethisterone acetate or isoflavonoids. Electrocardiogram was recorded in the supine position for 10 min. Spectral analysis included low and high frequencies in absolute (LF and HF) and normalized units (LFnu and HFnu), which are predominantly cardiac sympathetic modulation (CSM) and cardiac vagal modulation (CVM) indicators, respectively. The LF/HF ratio was also calculated. Symbolic analysis involved the following indexes: 0V % (CSM indicator), 1V % (CSM and CVM indicators), 2LV % (predominantly CVM indicator) and 2UV % (CVM indicator). Shannon and conditional entropies were also calculated.
  
  
  RESULTS
  Spectral analysis demonstrated that HRT affected HRV. LF, LFnu and LF/HF ratio were higher (showing increased CSM), while HFnu was lower (representing decreased CVM) in G2 than in G1. Correlations between complexity indices and HFnu were significant and positive only in G1.
  
  
  CONCLUSIONS
  Women undergoing HRT presented higher CSM and lower CVM than those who were not. Moreover, the expected positive relationship between CVM and complexity of HRV was found only in control group, thus indicating that CVM in women under therapy drop below a minimal value necessary to the association to become apparent, suggesting an unfavorable cardiac autonomic modulation in spite of HRT.
authors: Cardiovascular Physical Therapy Laboratory, Nucleus of Research in Physical Exercise (NUPEF), Department of Physical Therapy, Federal University of São Carlos, UFSCar, Via Washington Luiz, km 235, São Carlos, SP, 13565-905, Brazil.
authors: Natália Maria
authors: NM
authors: Perseguini
authors: Anielle Cristhine
authors: AC
authors: de Medeiros Takahashi
authors: Juliana Cristina
authors: JC
authors: Milan
authors: Patrícia Rehder
authors: PR
authors: dos Santos
authors: Valéria Ferreira Camargo
authors: VF
authors: Neves
authors: Audrey
authors: A
authors: Borghi-Silva
authors: Ester
authors: E
authors: Silva
authors: Nicola
authors: N
authors: Montano
authors: Alberto
authors: A
authors: Porta
authors: Aparecida Maria
authors: AM
authors: Catai
mesh_terms: D000368:Aged; D001341:Autonomic Nervous System / Q000187:drug effects*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D004967:Estrogens / Q000627:therapeutic use*; D005260:Female; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D008875:Middle Aged
chemical_list: D004967:Estrogens