title: Parasympathetic dysautonomia precedes left ventricular systolic dysfunction in Chagas disease.
abstract: BACKGROUND
  Parasympathetic dysautonomia is an established feature of advanced Chagas cardiomyopathy. However, in the absence of cardiac involvement, the presence of vagal dysfunction remains controversial. In a cross-sectional study, we compared patients with Chagas disease without cardiac involvement and healthy individuals by three different methods to determine whether vagal dysfunction is present in the early phase of Chagas disease.
  
  
  METHODS
  Sixty-one patients with Chagas disease without cardiac involvement and 38 controls were submitted to respiratory sinus arrhythmia test and 24-hour Holter monitoring. Vagal heart influences were assessed by the expiratory/inspiratory (E/I) ratio, time-domain indexes of heart rate variability (HRV), and by the quantification of a 3-dimensional return map.
  
  
  RESULTS
  The two groups were comparable in terms of left ventricular ejection fraction and left ventricular end-diastolic dimension. Compared with the control group, patients with Chagas disease had significantly lower values of the E/I ratio (mean +/- SD: 1.38 +/- 0.02 and 1.25 +/- 0.02, P <.004) and short-term indexes of HRV (median [interquartile range]-rMSSD: 23 [18-27] and 17 [13-23], P =.00; pNN50: 11 [7-17] and 6 [2-12], P =.00). P(3), a beat-to-beat HRV index derived from the 3-dimensional return map, also was significantly reduced in the Chagas disease group (mean +/- SD: 118 +/- 5 vs 100 +/- 4, P =.00). None of these indexes of vagal heart control were significantly correlated with left ventricular function or to the presence of esophageal radiologic abnormalities.
  
  
  CONCLUSIONS
  Parasympathetic dysautonomia is an independent and early phenomenon in Chagas disease and may precede left ventricular systolic dysfunction.
authors.affiliation: Hospital das Clínicas and School of Medicine, Federal University of Minas Gerais, Rua Companha, 98/101, 30310-770, Belo Horizonte, MG, Brazil. antonior@net.em.com.br
authors.forename: A L
authors.initials: AL
authors.lastname: Ribeiro
authors.forename: R S
authors.initials: RS
authors.lastname: Moraes
authors.forename: J P
authors.initials: JP
authors.lastname: Ribeiro
authors.forename: E L
authors.initials: EL
authors.lastname: Ferlin
authors.forename: R M
authors.initials: RM
authors.lastname: Torres
authors.forename: E
authors.initials: E
authors.lastname: Oliveira
authors.forename: M O
authors.initials: MO
authors.lastname: Rocha
mesh_terms: D000293:Adolescent; D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000209:etiology / Q000503:physiopathology*; D014355:Chagas Disease / Q000150:complications / Q000503:physiopathology*; D002940:Circadian Rhythm; D018450:Disease Progression; D015150:Echocardiography, Doppler; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate; D006352:Heart Ventricles / Q000294:innervation* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume; D013599:Systole; D014630:Vagus Nerve / Q000503:physiopathology*; D018487:Ventricular Dysfunction, Left / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*