Comparison of QT dispersion during atrial fibrillation and sinus rhythm in the same patients, at normal and prolonged ventricular repolarization

Aims Drug-induced increase in QT dispersion has been associated with increased risk of ventricular proarrhythmia. The aim of the present study was to compare QT dispersion during atrial fibrillation and sinus rhythm in the same patients at normal and prolonged ventricular repolarization. Methods and Results Sixty-one patients who had had chronic atrial fibrillation for 8±14 months received a 6 h infusion of the Ikr-blocker almokalant, the first 90 min of which are used for this analysis. The following day, after conversion to sinus rhythm, by almokalant (n=19) or direct current cardioversion (n=42), an identical 90 min infusion was administered. Prior to infusion, there was no difference in precordial QT dispersion between atrial fibrillation and sinus rhythm (29±12 vs 36±17 ms, P=ns). During infusion, at prolonged repolarization, the increase in QT dispersion was greater during sinus rhythm than during atrial fibrillation (58±49 vs 30±15 ms,P =0·0011, after 30 min infusion). No correlation was found between QT dispersion and the QT or RR interval. Conclusion QT dispersion during atrial fibrillation does not differ from QT dispersion during sinus rhythm during normal repolarization, while measurement of QT dispersion during prolonged repolarization, induced by an Ikr-blocker, yielded larger values during sinus rhythm than during atrial fibrillation.