Repolarization Abnormality for Prediction of All‐Cause and Cardiovascular Mortality in American Indians: The Strong Heart Study

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Abstract
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. 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). Novel descriptors of T-wave complexity provide additional prognostic information beyond QTc and PCA ratio for prediction of all-cause and CV mortality.