| Abstract: | Background: QT dispersion, measured as interlead variability of QT intervals in the surface electrocardiogram, has been demonstrated to provide an indirect measurement of the inhomogeneity of myocardial repolarization as a potential substrate for ventricular arrhythmias. Methods: QT dispersion was measured in the standard 12-lead ECG in 51 patients at the time of implantation of a third generation implantable cardioverter defibrillator (ICD) with automatic electrogram storage capability for electrical events triggering device therapy. In addition, QT dispersion was measured in 100 age- and sex-matched healthy controls. All 5 1 study patients with ICD were prospectively followed to determine possible associations between QT dispersion at implant and subsequent spontaneous ICD shocks for ventricular tachyarrhythmias (VT). Results: Rate-corrected QT dispersion and adjusted QTc dispersion, which takes account of the number of leads measured, were significantly greater in ICD patients compared to controls (76 ± 25 ms vs 46 ± 11 ms, and 24 ± 7 ms vs 14 ± 3 ms respectively, P < 0.0 1). During 15 ± 8 months follow-up, ventricular tachyarrhythmias occurred in 23 (45%) of 51 ICD patients. QTc dispersion and adjusted QTc dispersion were not significantly different between ICD patients with ventricular tachyarrhythmias and ICD patients without ventricular tachyarrhythmias during follow-up (74 ± 19 ms versus 77 ± 29 ms, and 23 ± 6 ms vs 25 ± 8 ms respectively). Conclusion: Increased QT dispersion measured in the 12-lead standard ECG does not appear to be a useful marker for future arrhythmic events in a mixed patient population with ICD. |
