Beat-to-beat variation of three-dimensional QRS-T angle measures during exercise test

Dynamical beat-to-beat behavior of the spatial QRS-T angle features is largely unknown. In this study, an automatic beat-to-beat method for calculating the features from standard 12-lead ECG was developed, and the variability of three QRS-T angle measures (TCRT, cos(QRST-angle), and cos(PlaneAngle)) during an incremental exercise on a bicycle ergometer was specified. The trend of the TCRT during exercise was negative, and it was more negative in healthy subjects (n=10) compared to coronary artery disease (CAD) patients (n=10), p-value was 0.01 between the groups. However, all the QRS-T angle measures did not appear to behave similarly, and therefore, they should not be paralleled with each other. In addition, beat-to-beat variability of all the QRS-T-angle measures was so extensive, that it should be taken into account when considering the reliability of one-beat analyses of the angle measures.