Cardiac repolarisation can be detected as an ordered spatial process on the body surface

Cardiac repolarisation abnormalities may be the mechanism for unstable heart rhythms such as ventricular fibrillation. Clinical measures of repolarisation have been limited to electrocardiogram (ECG) repolarisation duration and dispersion. Measures from T wave shape might provide useful clinical data and a better understanding for modelling the conduction processes. The aim of this work was to explore the measurement of subtle changes in the shape of the T wave over the body surface. Measurements of T wave amplitude, symmetry and peak location in precordial leads of the ECG were made on five normal subjects and five cardiac patients. T wave symmetry changed from a mean of 1.0 for V1 to 1.7 for V6 in the normal subjects, and from 1.5 to 2.8 in the patients. The position of the T wave peak changed by a mean of 39 ms from V1 to V6 for the normal subjects, and by 44 ms for the patients. Further, differences in shape between adjacent leads were evident, especially between V2 and V3. The results suggest that repolarisation is smooth and ordered. There are measurable changes in T wave shape across the leads which will allow the validation of computer models of cardiac repolarisation.