title: Spatial repolarization heterogeneity and survival in Chagas disease.
abstract: OBJECTIVE
  We investigated if cardiac spatial repolarization heterogeneity might be associated with an increased risk of death in patients with chronic Chagas disease.
  
  
  METHODS
  Repolarization heterogeneity was assessed using the V-index, a recently introduced metric founded on a biophysical model of the ECG. This metric provides an estimate of the standard deviation of the repolarization times across the heart. We analyzed 113 patients (aged 21- 67 years) enrolled between 1998 and 1999 who had a known serological status showing positive reactions to Trypanosoma cruzi. Fourteen subjects died during a 10-year follow-up period.
  
  
  RESULTS
  The V-index was significantly lower in survivor (S) than in non-survivor (NS) subjects (S: 31.2 ± 13.3 ms vs NS: 41.2 ± 18.6 ms, single-tail t-test: p = 0.009, single-tail Wilcoxon rank sum test: p = 0.029). A V-index larger than 36.3 ms was related to a significantly higher risk of death in a univariate Cox proportional-hazards analysis (hazard ratio, HR = 5.34, p = 0.0046). In addition, V-index > 36.3 ms retained its prognostic value in a multivariate Cox proportional-hazards analysis after adjustment for other three clinical variables (left ventricular ejection factor < 0.50, QRS duration > 133 ms, ventricular tachycardia during stress testing or 24 hours Holter) and for T-wave amplitude variability > 30 μV, even using shrinkage, a statistical procedure that protects against over-fitting due to small sample size.
  
  
  CONCLUSIONS
  The study showed that an increased dispersion of repolarization times in patients with Chagas disease, as measured by the V-index, is significantly correlated with the risk of death in a univariate survival analysis. The V-index captures prognostic information not immediately available from the analysis of other established risk factors.
authors: Roberto Sassi, Dipartimento di Informatica, Università degli Studi di Milano, Via Bramante 65, 26013 Crema (CR), Italy, E-mail: roberto.sassi@unimi.it.
authors: R
authors: R
authors: Sassi
authors: M W
authors: MW
authors: Rivolta
authors: L T
authors: LT
authors: Mainardi
authors: R C
authors: RC
authors: Reis
authors: M O C
authors: MO
authors: Rocha
authors: A L P
authors: AL
authors: Ribeiro
authors: F
authors: F
authors: Lombardi
mesh_terms: D000328:Adult; D000368:Aged; D002598:Chagas Cardiomyopathy / Q000401:mortality* / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory / Q000706:statistics & numerical data*; D005260:Female; D005500:Follow-Up Studies; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D032383:Myocytes, Cardiac / Q000502:physiology*; D011379:Prognosis; D016016:Proportional Hazards Models; D012306:Risk; D012815:Signal Processing, Computer-Assisted; D016019:Survival Analysis; D014693:Ventricular Fibrillation / Q000401:mortality / Q000503:physiopathology*; D055815:Young Adult
keywords: Chagas cardiomyopathy; Chagas disease; ambulatory electrocardiography; digital signal processing; electrophysiological processes; ventricular fibrillation