Stability of qt measurements in the PTB database depending on the selected lead

Prolonged QT interval is considered as an index of propensity to dangerous ventricular tachyarrhythmias. The Physionet/CinC challenge 2006 encourages teams to automatically measure the QT interval of lead Il\´s first representative beat in every record of the PTB database. A "median self-centering approach" based on manual entries to the challenge is used for evaluation of algorithms. We participated in the challenge using a single-lead wavelet based delineator. The selection of the representative beat was performed using information from several beats and the available leads. A score of 19.22 ms was obtained. Additionally the stability of the delineation in the different leads is studied. Comparing the QT measurement stability in 10 consecutive beats, we found significant inter-lead differences. The most stable QT measurements were found in precordial leads V2-V4, while frontal leads are those with greatest measurement variance. Leads with more stable QT were also those with maximum Twave amplitude.