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

Aims Drug-induced increase in QT dispersion has been associated with increa sed risk of ventricular proarrhythmia. The aim of the present study was to compare QT dispersion during atrial fibrillation and sinus rhythm in the sa me patients at normal and prolonged ventricular repolarization. Methods and Results Sixty-one patients who had had chronic atrial fibrillat ion for 8 +/- 14 months received a 6 h infusion of the I-kr-bIocker almokal ant, the first 90 min of which are used for this analysis. The following da y, after conversion to sinus rhythm, by almokalant (n = 19) or direct curre nt cardioversion (n = 42), an identical 90 min infusion was administered. P rior to infusion, there was no difference in precordial QT dispersion betwe en atrial fibrillation and sinus rhythm (29 +/- 12 vs 36 +/- 17 ms, P = ns) . During infusion, at prolonged repolarization, the increase in QT dispersi on 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 measure ment of QT dispersion during prolonged repolarization, induced by an I-kr-b locker, yielded larger values during sinus rhythm than during atrial fibril lation. (C) 2000 The European Society of Cardiology.