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

Background: T-wave morphology parameters based on principal component analysis (PCA) are can-didate 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. A.N.E. 2007;12(4):354–363 ECG; QT interval; principal component analysis; repeatabilit