title: Heart rate variability in myotonic dystrophy type 1 patients.
abstract: BACKGROUND
  Cardiac involvement is common in myotonic dystrophy (MD) patients. Heart rate variability (HRV) is a simple and reliable technique that can be useful for studying the influence of the autonomic nervous system on the heart.
  
  
  OBJECTIVE
  Study heart rate variability in patients with type 1 MD.
  
  
  METHODS
  We studied HRV during 5-minute recordings in MD patients and in a healthy control group. We analyzed frequency domains (LF and HF) in normalized units (nu) and sympathovagal balance, in the sitting and supine position.
  
  
  RESULTS
  Seventeen patients (10 men and 7 women) and seventeen matched healthy individuals (10 men and 7 women) were studied. Sympathetic and parasympathetic modulations of the heart increased in male MD patients from supine to sitting position in 19% of LFnu and the LF/HF ratio rose by 42.3%. In the sitting position, male MD patients exhibited significantly higher sympathovagal balances in 50.9% compared to healthy control individuals. HRV was influenced by both gender and disease. Gender influenced LFnu in the supine position while the LF/HF ratio and HFnu were affected in both positions. Post hoc analyses showed that gender significantly impacts MD patients and healthy individuals in different ways (p < 0.01). The low frequency domain in the sitting position (LFnu) was significantly influenced by the disease.
  
  
  CONCLUSIONS
  The results of this study suggest that the sympathetic drive in middle-aged male MD patients who are not severely impaired and present moderate disease duration seems to be greater than in healthy matched individuals.
authors.affiliation: Laboratório de Fisioterapia Pneumocardiovascular - Departamento de Fisioterapia - Centro de Ciências da Saúde - Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil. fregonezi@ufrnet.br
authors.forename: Guilherme
authors.initials: G
authors.lastname: Fregonezi
authors.forename: Thaise
authors.initials: T
authors.lastname: Araújo
authors.forename: Mario Emilio
authors.initials: ME
authors.lastname: Dourado Junior
authors.forename: Joceline
authors.initials: J
authors.lastname: Ferezini
authors.forename: Ester
authors.initials: E
authors.lastname: Silva
authors.forename: Vanessa
authors.initials: V
authors.lastname: Resqueti
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000502:physiology; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000503:physiopathology*; D012737:Sex Factors; D013997:Time Factors