Spatial, temporal and wavefront direction characteristics of 12-lead T-wave morphology

Three new approaches for the analysis of ventricular repolarisation in 12-l ead electrocardiograms (ECGs) are presented: the spatial and temporal varia tions in T-wave morphology and the wavefront direction difference between t he ventricular depolarisation and repolarisation waves. The spatial variati on characterises the morphology differences between standard leads. The tem poral variation measures the change in interlead relationships. A minimum d imensional space, constructed by ECG singular value decomposition, is used. All descriptors are measured using the ECG vector in the constructed space and the singular vectors that define this space. None of the descriptors r equires time domain measurements (e.g. the precise detection of the T-wave offset), and so the inaccuracies associated with conventional QT interval r elated parameters are avoided. The new descriptors are compared with the co nventional measurements provided by a commercial system for an automatic ev aluation of QT interval and QT dispersion in digitally recorded 12-lead ECG s. The basic comparison uses a set of 1100 normal ECGs. The short-term intr asubject reproducibility of the new descriptors is compared with that of th e conventional measurements in a set of 760 ECGs recorded in 76 normal subj ects and a set of 630 ECGs recorded in 63 patients with hypertrophic cardio myopathy (ten serial recordings in each subject of both these sets). The di scriminative power of the new and conventional parameters to distinguish no rmal and abnormal repolarisation patterns is compared using the same set. T he results show that the new parameters do not correlate with the conventio nal QT interval-related descriptors (i.e. they assess different ECG qualiti es), are generally more reproducible than the conventional parameters, and lead to a more significant separation between normal and abnormal ECGs, bot h univariately and in multivariate regression models.