In preclinical trials, the QT interval is widely used to assess changes in repolarization. However, some drug treatments, like hERG blockers, have been associated with morphology changes in T waves. The semi-automated multi-species ECG analyzer ECG51a can be used to assess these changes.
Indeed, ECG51a allows to customize fiducial marks placed on the ECG beats and calculate amplitude, duration, slope and area under the curve between these points. In order to assess changes in T wave morphology, lists of marks and calculated data in ECG51a properties window are customized as indicated in the figures below. In practice, this is done using the editing toolbar on the lower left of each dedicated tab in ECG51a properties window.
After ECG51a analysis and data extraction into Excel, the following parameters can be obtained:
- Asymmetry : Slopes of the ascending and descending parts of the T-wave are output by ECG51a and extracted in Excel from the NSS data file. Asymmetry is then calculated in Excel as the average of the square of the difference between both slopes.
- Notches : The amplitude of a notch is output by ECG51a. It is then extracted in Excel and normalized with T peak amplitude. T waves can be sorted into three categories: no deflection, moderate notch (perceptible bulge) and pronounced notch (distinct protuberance above the apex).
- T wave area : The area under the curve of the T wave is output by ECG51a and extracted in Excel.
- Tpeak to Tend interval, which represents the transmural dispersion of repolarization can also be output by ECG51a and extracted in Excel.
- T wave height-to-width ratio : The T wave height and the T wave duration are extracted in Excel, then the ratio of both values is calculated in Excel, to provide a measure of the T wave flatness.
More studies are needed to determine the potential value of T wave morphology changes for torsade de pointes risk assessment.