Repolarization characteristics and incidence of Torsades de Pointes in patients with acquired complete atrioventricular block.

OBJECTIVE: Torsades de pointes (TdP) during bradyarrhythmias have been reported to be associated with gender, degree of QT prolongation and duration of bradyarrhythmia. We sought to investigate the repolarization characteristics on 12-lead electrocardiogram (ECG) and the incidence of TdP in patients with acquired complete atrioventricular block (CAVB).

METHODS: Fifty consecutive patients with acquired CAVB were included in the study. Patients with coronary artery disease, systolic dysfunction and previous cardiac surgery were excluded. Patients were monitored during hospitalization for ventricular arrhythmias (VA). Serum potassium, magnesium, calcium levels and thyroid-stimulating hormone were measured. Heart rate, QRS duration, QT/QTc, JT/JTc and Tpeak-Tend intervals were measured. Pathologic U waves, T-U complex, and QT morphologies were remarked.

RESULTS: Patients presented with presyncope (n=39, 78%), syncope (n=12, 24%), and palpitations (n=8, 16%). All patients were in sinus rhythm. Duration of CAVB was 8.5 days (median). Patients were divided into two groups based on JT interval. Group 1 (JT=or>500 ms, n=13) tended to have more female patients and more VAs in comparison to Group 2 (JT<500 ms, n=37). Group 1 patients had more pathologic U waves and T-U complexes, longer Tpeak-Tend intervals, and more long QT2 syndrome (LQT2)-like QT morphology in comparison to Group 2 patients. Group 2 patients had more often syncope. One patient in Group 2 developed ventricular fibrillation in the presence of hypokalemia and hypomagnesemia.

CONCLUSION: Torsades de Pointes during CAVB was rare among our patient population. The predictors of VA during CAVB were presence of prolonged QTc/JTc intervals, pathologic U wave and T-U complex, prolonged Tpeak-Tend interval, and LQT2-like QT morphology.