Analysis of multi-lead QT dispersion by means of an algorithm implemented on Labview

An algorithm was developed to measure both QT interval and QT dispersion. To check the accuracy of the algorithm, 25 single channel ECGs were recorded and their QT intervals were computed. Three lead ECG data were then recorded and their QT dispersions were statistically analyzed. The algorithm was then used to study the effect of the electric dipole of the heart on QT dispersion. It was hypothesized that QT dispersion is influenced by the electric field caused by the heart dipole. If the RA (right arm) and LA (left arm) electrodes were placed over the wrists and RL (right leg) and LL (left leg) electrodes over the ankles, the resulting QT dispersion of leads I, II and III would be expected to be smaller than if the electrodes were placed on the shoulders and below the chest cavity. This would be due to the electric field of the heart dipole attenuating with an increasing distance from the dipole center. It was found that the mean QT intervals were consistent with the results in the literature and the mean and the standard deviation of the resulting QT dispersions were significantly smaller than those found in previous studies. In near and fat field analysis, subjecting the data to a student´s T test revealed that both near and far field QT dispersion data were drawn from the same population