title: Cardiac autonomic modulation in hypertensive patients with Chagas' disease.
abstract: BACKGROUND
  Arterial hypertension and Chagas' disease are prevalent pathologies in Latin America. It has been demonstrated that each one of them may cause cardiac autonomic dysfunction. This study aimed to investigate the pattern of cardiac autonomic modulation in chagasic-hypertensive patients.
  
  
  METHODS
  Subjects (n=120) without left ventricular dysfunction were distributed in four groups: healthy control (n=30); hypertensive (n=30); chagasic (n=30) and chagasic-hypertensive (n=30). Patients were evaluated by autoregressive spectral analysis of heart rate variability in three different conditions: baseline, cold face and passive tilt tests. Power spectral densities in low (0.04-0.15 Hz) and high (0.15-0.50 Hz) frequency bands were estimated in both absolute and normalized units.
  
  
  RESULTS
  Baseline median values (percentile 25 to percentile 75) of mean arterial pressure (in mmHg) were 93.3 (85.0-96.7), 116.7 (*, #) (110.0-129.2), 86.7 (83.3-92.5) and 106.7 (*, #) (106.7-110.0) for healthy control, hypertensive, chagasic and chagasic-hypertensive patients, respectively (*p<0.05 versus healthy control, #p<0.05 against chagasic group). Heart rate at rest did not differ among groups. Regarding to spectral parameters in baseline conditions, the absolute power of high frequency component of heart rate variability of the chagasic-hypertensive group was significantly lower than that found in healthy control and hypertensive patients. There were no differences in spectral parameters responses during cold face test. After passive tilt test, however, decreases in high frequency oscillations and increases in sympathovagal balance (low and high frequency ratio) were significantly lower in hypertensive, chagasic and chagasic-hypertensive patients as compared with healthy control.
  
  
  CONCLUSIONS
  These data indicate that chagasic-hypertensive patients presented an impairment of cardiac parasympathetic modulation at baseline conditions as well as in response to passive orthostatic stress.
authors.affiliation: Faculdade de Medicina do Triângulo Mineiro, Disciplina de Doenças Infecciosas e Parasitárias, Departamento de Clínica Médica, Avenida Getúlio Guarita, S/N, Caixa Postal: 118, Uberaba, Minas Gerais 38025-440, Brazil.
authors.forename: Adriana Nazaré
authors.initials: AN
authors.lastname: Miziara
authors.forename: Rodrigo Juliano
authors.initials: RJ
authors.lastname: Molina
authors.forename: Bruno Doriguetto Couto
authors.initials: BD
authors.lastname: Ferreira
authors.forename: Carlos José Dornas G
authors.initials: CJ
authors.lastname: Barbosa
authors.forename: Valdo José
authors.initials: VJ
authors.lastname: Dias da Silva
authors.forename: Aluízio
authors.initials: A
authors.lastname: Prata
authors.forename: Dalmo
authors.initials: D
authors.lastname: Correia
mesh_terms: D000328:Adult; D000818:Animals; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001794:Blood Pressure; D001938:Brazil; D002319:Cardiovascular System / Q000294:innervation / Q000503:physiopathology*; D014355:Chagas Disease / Q000150:complications* / Q000503:physiopathology; D003080:Cold Temperature; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D006973:Hypertension / Q000150:complications* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric; D018667:Tilt-Table Test