Method for the measurement of the QT and T-wave duration and beat-to-beat variability

The QT interval duration is an important non-invasive electrophysiological parameter that reflects ventricular depolarization and repolarization time. A knowledge of QT variability also provides specific information on the normal and pathological ventricular myocardium, and the influence of the autonomic nervous system. A numerical algorithm was developed for measuring QT interval and T-wave duration in the surface electrocardiogram. In comparison with numerous other approaches, this method calculates these durations without averaging of QRS complexes on a beat-to-beat basis. The main aim of this study was to assess the efficacy of this method for characterizing cardiac diseases. In 6 patients with hypertrophic cardiomyopathy and a control group of 5 healthy, age-matched subjects, different interval durations were calculated. In contrast to the mean QT interval duration, only the T-wave duration differed significantly between the two groups.