title: Prognostic value of QT interval parameters for mortality risk stratification in Chagas' disease: results of a long-term follow-up study.
abstract: BACKGROUND
  QT interval parameters are potential prognostic markers of arrhythmogenicity risk and cardiovascular mortality and have never been evaluated in Chagas' disease.
  
  
  RESULTS
  Outpatients (738) in the chronic phase of Chagas' disease were enrolled in a long-term follow-up study. Maximal heart rate-corrected QT (QTc) and T-wave peak-to-end (TpTe) intervals and QRS, QT, JT, QTapex, and TpTe dispersions and variation coefficients were measured manually and calculated from 12-lead ECGs obtained on admission. Clinical, radiological, and 2-dimensional echocardiographic data were also recorded. Primary end points were all-cause, Chagas' disease-related, and sudden cardiac mortalities. During a follow-up of 58+/-39 months, 62 patients died, 54 of Chagas' disease-related causes and 40 suddenly. Multivariate Cox survival analysis revealed that the QT-interval dispersion (QTd) (hazard ratio, 1.45; 95% confidence interval, 1.29 to 1.63; P<0.001, for 10-ms increments) and left ventricular (LV) end-systolic dimension (hazard ratio, 1.36; 95% confidence interval, 1.21 to 1.53; P<0.001, for 5-mm increments) were the strongest independent predictors for all end points. The maximum QTc interval (QTcmax) could substitute for QTd with a worse predictive performance. Other predictors were heart rate, presence of pathological Q waves, frequent premature ventricular contractions (PVCs), and isolated left anterior fascicular block (LAFB) on the ECGs. Kaplan-Meier survival curves demonstrated that a QTd > or =65 ms or a QTcmax > or =465 ms1/2 discriminated the 2 groups with significantly different prognoses.
  
  
  CONCLUSIONS
  Electrocardiographic QTd and echocardiographic LV end-systolic dimension were the most important mortality predictors in patients with Chagas' disease. Heart rate, the presence on ECG of pathological Q waves, frequent PVCs, and isolated LAFB refined the mortality risk stratification.
authors.affiliation: Department of Internal Medicine, Clementino Fraga Filho University Hospital, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil. gilsalles@hucff.ufrj.br
authors.forename: Gil
authors.initials: G
authors.lastname: Salles
authors.forename: Sergio
authors.initials: S
authors.lastname: Xavier
authors.forename: Andrea
authors.initials: A
authors.lastname: Sousa
authors.forename: Alejandro
authors.initials: A
authors.lastname: Hasslocher-Moreno
authors.forename: Claudia
authors.initials: C
authors.lastname: Cardoso
mesh_terms: D001938:Brazil / Q000453:epidemiology; D002598:Chagas Cardiomyopathy / Q000175:diagnosis* / Q000401:mortality* / Q000503:physiopathology; D014355:Chagas Disease / Q000401:mortality* / Q000503:physiopathology*; D002908:Chronic Disease; D015897:Comorbidity; D016757:Death, Sudden, Cardiac / Q000453:epidemiology; D018450:Disease Progression; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010045:Outpatients / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D015203:Reproducibility of Results; D018570:Risk Assessment; D016019:Survival Analysis; D013995:Time