title: Baroreflex sensitivity and its association with arrhythmic events in Chagas disease.
abstract: BACKGROUND
  Sudden death is the leading cause of death in Chagas disease (CD), even in patients with preserved ejection fraction (EF), suggesting that destabilizing factors of the arrhythmogenic substrate (autonomic modulation) contribute to its occurrence.
  
  
  OBJECTIVE
  To determine baroreflex sensitivity (BRS) in patients with undetermined CD (GI), arrhythmogenic CD with nonsustained ventricular tachycardia (NSVT) (GII) and CD with spontaneous sustained ventricular tachycardia (STV) (GIII), to evaluate its association with the occurrence and complexity of arrhythmias.
  
  
  METHODS
  Forty-two patients with CD underwent ECG and continuous and noninvasive BP monitoring (TASK force monitor). The following were determined: BRS (phenylephrine method); heart rate variability (HRV) on 24-h Holter; and EF (echocardiogram).
  
  
  RESULTS
  GIII had lower BRS (6.09 ms/mm Hg) as compared to GII (11.84) and GI (15.23). The difference was significant between GI and GIII (p = 0.01). Correlating BRS with the density of ventricular extrasystoles (VE), low VE density (<10/h) was associated with preserved BRS. Only 59% of the patients with high VE density (> 10/h) had preserved BRS (p = 0.003). Patients with depressed BRS had higher VE density (p = 0.01), regardless of the EF. The BRS was the only variable related to the occurrence of SVT (p = 0.028).
  
  
  CONCLUSIONS
  The BRS is preserved in undetermined CD. The BRS impairment increases as disease progresses, being more severe in patients with more complex ventricular arrhythmias. The degree of autonomic dysfunction did not correlate with EF, but with the density and complexity of ventricular arrhythmias.
authors.forename: Astrid Meireles
authors.initials: AM
authors.lastname: Santos
authors.forename: Mauricio Ibrahim
authors.initials: MI
authors.lastname: Scanavacca
authors.forename: Francisco
authors.initials: F
authors.lastname: Darrieux
authors.forename: Bárbara
authors.initials: B
authors.lastname: Ianni
authors.forename: Sissy Lara de
authors.initials: SL
authors.lastname: Melo
authors.forename: Cristiano
authors.initials: C
authors.lastname: Pisani
authors.forename: Francisco
authors.initials: F
authors.lastname: Santos Neto
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sosa
authors.forename: Denise Tessariol
authors.initials: DT
authors.lastname: Hachul
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D017704:Baroreflex / Q000502:physiology*; D014355:Chagas Disease / Q000503:physiopathology*; D016757:Death, Sudden, Cardiac; D018450:Disease Progression; D015150:Echocardiography, Doppler; D015716:Electrocardiography, Ambulatory; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013318:Stroke Volume / Q000502:physiology; D013997:Time Factors