Usefulness of beat-to-beat QT dispersion fluctuation for identifying patients with coronary heart disease at risk for ventricular arrhythmias

QT dispersion (QTd) has been proposed as a marker of ventricular repolarization inhomogeneity and arrhythmic risk, but despite the dynamic properties of ventricular repolarization and the fact that QTd represents only a static parameter of the repolarization event, beat-to-beat QTd behavior has not been assessed so far. Beat-to-beat QTd was automatically measured in 12-lead digitized electrocardiographic recordings obtained over 10 minutes from 77 subjects. Forty-seven patients had coronary heart disease without a history of ventricular arrhythmias, 12 had coronary heart disease and documented ventricular tachycardia, and 18 were normal subjects. Mean QTd, the difference between the maximum minus the minimum QTd observed over the recording time (QTd variation), the maximum difference of QTd between consecutive beats (QTd maximum), and QTd SD (QTd variability) were analyzed between groups. The temporal QTd parameters were significantly increased in the group of patients with susceptibility to ventricular arrhythmias compared with those in both healthy subjects (QTd variation p <0.0001, QTd maximum p <0.001, QTd variability p <0.0001) and patients without a history of ventricular tachycardia (QTd variation p <0.01, QTd maximum p <0.01, QTd variability p <0.01). Mean QTd was also significantly increased in the groups of patients with and without ventricular tachycardia compared with controls (p <0.001 and <0.01), but did not differ significantly between the 2 patient groups. Thus, QTd has a dynamic behavior with significant beat-to-beat fluctuations even in normal subjects and is more marked in patients with coronary heart disease at risk for ventricular arrhythmias.