Dispersion in ventricular repolarization in patients with severe intraventricular conduction disturbances

Increased dispersion of repolarization, measured invasively or by QT interval measurements, is associated with an increased risk for ventricular arrhythmias and sudden death. Most studies on this issue have included patients with normal intraventricular conduction, and it is not known if this finding has a predictive value also in patients with intraventricular conduction disorders. An invasive electrophysiological study, including programmed ventricular stimulation and assessment of effective refractory periods at two RV sites, was performed in 103 patients with bifascicular block (mean age 67 +/- 12 years). QT dispersion was measured from standard 12-lead ECGs. In patients with inducible sustained polymorphic VT or VF the dispersion in refractoriness between the two RV sites was significantly greater (46 +/- 11 ms, n = 13) than in noninducible patients (14 +/- 14 ms, n = 84) and in patients with inducible sustained monomorphic VT (16 +/- 5 ms, n = 6) (P < 0.01). Similarly, QT dispersion was 104 +/- 46 ms, 66 +/- 31 ms, and 77 +/- 33 ms, respectively, in the three groups (P < 0.05). Dispersion in repolarization, neither measured invasively nor by QT interval measurements, predicted sudden death, all cause mortality, or ventricular arrhythmia during a mean follow-up period of 3 years. In patients with bifascicular block, there is a relation between the degree of dispersion of ventricular repolarization and the inducibility of polymorphic ventricular arrhythmia, but this outcome did not occur during follow-up.