Ambulatory electrocardiographic evidence of transmural dispersion of repolarization in patients with long-QT syndrome type 1 and 2.

Background: Transmural dispersion of repolarization (TDR) may be related to the genesis of torsade de pointes (TdP) in patients with the long-QT (LQT) syndrome. Experimentally, LQT2 models show increased TDR compared with LQT1, and beta-adrenergic stimulation increases TDR in both models. Clinically, LQT1 patients experience symptoms at elevated heart rates, but LQT2 patients do so at lower rates.

Importance of using standard rather than torso surface electrocardiographic leads for pacemapping at the right ventricular outflow tract.

Although pacemapping has been used to localize the origin of ventricular tachycardia, the effect of changes in the position of ECG electrodes during ventricular pacing remains unknown. To clarify the relationship between the position of ECG limb electrodes and QRS configuration during pacemapping at the right ventricular outflow tract (RVOT), RVOT pacing was performed on 12 patients at eight pacing sites located in the anterior, septal, lateral, and posterior portions each in the high and low RVOT. Standard and torso ECGs were recorded simultaneously during each pacing protocol, and the QRS axis and amplitude were compared between the two ECGs.