T‐Wave Morphology Parameters Based on Principal Component Analysis Reproducibility and Dependence on T−Offset Position

Abstract

Background: T-wave morphology parameters based on principal component analysis (PCA) are candidate to better understand the relation between QT prolongation and torsades de pointes. We aimed to assess the repeatability and to determine the influence of T-end position on PCA parameters.Methods: Digital ECGs recorded from 30 subjects were used to assess short term (5 minutes), circadian and long-term (28 days) repeatability of PCA parameters. The T-end cursor position was moved backward and forward ( ± 8 ms) from its optimal position. We calculated QRS-T angle, PCA ratio, and T-wave residuum (TWR).Results: At long-term evaluation, coefficients of variation were 11.3 ± 9.9%, 11.7 ± 7.1%, and 23.0 ± 22.0% for the QRS-T angle, PCA ratio, TWR, respectively. After moving the T-end cursor, repeatability was 0.42 ± 0.2%, 1.00 ± 1.04%, 4.0 ± 4.2% for the same PCA parameters.Conclusions: T-wave morphology parameters based on PCA are reproducible with the exception of TWR and QRS-T angle. In addition, PCA is robust, showing only little dependence on T-end cursor position. These data should be taken into account for safety pharmacology trials.

Quantitative Assessment of Vectorcardiographic Loop Morphology

“…VCG loop morphology can be characterized by the direction and amplitude of the instantaneous initial spatial [3] and maximum “peak” and “mean” vectors of the loop [4]. The “roundness” or principal shape of the loop has been described as the ratio of VCG loop height and width [5], or as the ratio of the second and first principal components of the orthogonal eigenvectors [6]. It has been shown that normal hearts have QRS loops which stay primarily in a single “main,” or “preferential” plane [7; 8].…”

Detection of Extra Components of T Wave by Independent Component Analysis in Congenital Long-QT Syndrome

“…20,21 Principal component analysis also was reported to be useful in prediction of cardiovascular mortality. 22 So far, ICA has not been applied for analysis of the repolarization process in LQTS.…”

“…As a multivariate analysis of inhomogeneity of ventricular repolarization, the principal component analysis has been applied for the assessment of T-wave morphology in LQTS by some investigators, 20,21 the results of which demonstrated its usefulness in distinguishing abnormal from normal repolarization processes such that a high second/first eigenvector ratio predicts increased inhomogeneous repolarization. 20,21 Principal component analysis also was reported to be useful in prediction of cardiovascular mortality.…”

Beat-to-beat determinants of the beat-to-beat temporal and spatial variability of repolarization

“…Spatial T-loop roundness was quantified via principal component analysis (PCA)[12]. For each T loop, the two most significant components accounted for the length and width of the loop, respectively.…”