Effects of the ventricular activation sequence on the JT interval.

In a retrospective and prospective analysis of electrocardiograms, we noted that the JT interval is not independent of the ventricular depolarization pattern, but is paradoxically shorter for wider QRS morphologies. Such an affect on the JT interval must be accounted for if it is to be used as an accurate means of following the duration of ventricular repolarization for clinical purposes, such as guidance of drug administration.