title: Repolarization abnormality for prediction of all-cause and cardiovascular mortality in American Indians: the Strong Heart Study.
abstract: BACKGROUND
  Analysis of electrocardiographic (ECG) repolarization abnormality using QTc interval and principal component analysis (PCA) of the T-wave vector predict all-cause and cardiovascular (CV) mortality. Novel descriptors of T-wave morphology have been suggested as measures of repolarization heterogeneity and adverse prognosis. However, whether these T-wave descriptors provide prognostic information beyond QTc and the PCA ratio has not been examined.
  
  
  RESULTS
  Predictive values of QTc, PCA, and novel ECG variables characterizing the T-wave loop were assessed in 1,729 American Indian participants in the first Strong Heart Study exam. T-loop morphology was quantified by the ratio of the second to first eigenvalues of the T-wave vector (PCA ratio), T-loop area (TLA) projected onto the dominant vector plane, T-wave morphology dispersion (TMD) and by the sum of the squares of the fourth to eighth eigenvalues, the T-wave residuum (TWR). After mean follow-up of 4.8 +/- 0.8 years, there were 183 deaths from all causes, including 51 CV deaths. In univariate Cox analyses, prolonged QTc, increased PCA ratio, TLA, TMD, and TWR were significant predictors of all-cause and CV mortality (P < 0.001). In multivariate Cox analyses adjusting for demographic and clinical risk factors for mortality, increased PCA ratio (chi-square = 7.9, P = 0.005) and TWR (chi-square = 5.3, P = 0.022) remained significant predictors of CV mortality and increased QTc (chi-square = 12.1, P < 0.001) and TWR (chi-square = 6.0, P = 0.014) of all-cause mortality. Addition of TWR to the model with clinical variables and the PCA ratio for CV mortality and to the model with clinical variables and prolonged QTc for all-cause mortality increased prognostic value of each model (increase in overall chi-square from 287.5 to 301.9 and from 221.5 to 230.3, respectively).
  
  
  CONCLUSIONS
  Novel descriptors of T-wave complexity provide additional prognostic information beyond QTc and PCA ratio for prediction of all-cause and CV mortality.
authors.affiliation: Greenberg Division of Cardiology, Department of Medicine, Weill Medical College of Cornell University, New York, New York 10021, USA. pokin@med.cornell.edu
authors.forename: Peter M
authors.initials: PM
authors.lastname: Okin
authors.forename: Marek
authors.initials: M
authors.lastname: Malik
authors.forename: Katerina
authors.initials: K
authors.lastname: Hnatkova
authors.forename: Elisa T
authors.initials: ET
authors.lastname: Lee
authors.forename: James M
authors.initials: JM
authors.lastname: Galloway
authors.forename: Lyle G
authors.initials: LG
authors.lastname: Best
authors.forename: Barbara V
authors.initials: BV
authors.lastname: Howard
authors.forename: Richard B
authors.initials: RB
authors.lastname: Devereux
mesh_terms: D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000401:mortality; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000208:ethnology / Q000401:mortality*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005260:Female; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D025341:Principal Component Analysis; D011379:Prognosis; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D015996:Survival Rate; D014481:United States / Q000453:epidemiology