Influence of T wave amplitude on automatic QT measurement

The aim was to investigate the influence of the T wave amplitude on 3 automatic QT measurement techniques. The subjects were 20 normals and 20 cardiac patients with arrhythmias and/or post myocardial infarction. 1 manual and 3 automatic algorithms were used to measure the QT interval from each of the 12 standard leads of each subject. The difference (denoted AQD) between the manual reference and automatic QT measurements was calculated. The amplitude of each T wave was also measured. The variability of AQD was found to fall for most techniques with greater T wave amplitude for both subject groups. The mean AQD is lower in the clinical vs normal subject groups for small T waves. It was concluded that T wave amplitude influences automatic QT measurement. However, since performance is different even when T amplitude is matched for normal and clinical ECGs this suggests additional morphological influences.