Cardiac depolarization and repolarization in Wolff-Parkinson-White syndrome

Abstract

Delta wave and QRS complex polarities have been extensively studied in preexcitation syndromes. However, only limited data exist about ventricular depolarization and repolarization in the setting of maximal preexcitation in relation to the site of insertion of the accessory pathway. Therefore this study was designed to systematically analyze cardiac depolarization and repolarization in patients with maximal preexcitation. We analyzed the polarity of the QRS complex and T wave on the frontal plane on the conventional 12-lead electrocardiogram in 118 patients with maximal preexcitation. Fast atrial pacing was used to provoke maximal ventricular preexcitation. The 32 patients with a left lateral accessory pathway showed right-axis deviation of the QRS complex (110 ± 20 degrees) with a left-axis deviation of the T-wave axis (−40 ± 25 degrees). The 54 patients with a posteroseptal accessory pathway had a left axis of the QRS complex (−50 ± 20 degrees) with a right-axis deviation of the T-wave axis (95 ± 15 degrees). The 11 patients with a right lateral accessory pathway had a left axis of the QRS complex (−40 ± 20 degrees) and a right axis of the T wave (110 ± 10 degrees).In 7 patients with a left anterolateral accessory pathway and 14 patients with a right anteroseptal accessory pathway, the axis of the QRS complex was 50 ± 25 degrees and 45 ± 20 degrees, respectively. T-wave polarity, however, showed two distinct patterns with a vertically directed T-wave axis (60 ± 25) in left anterolateral pathways and a T-wave axis directed in the upper right quadrant (−145 ± 20) in right anteroseptal pathways. In conclusion, electrocardiographic analysis of ventricular depolarization and repolarization in Wolff-Parkinson-White syndrome revealed characteristic polarities for the QRS complex and T wave depending on accessory pathway localization. These data are helpful in noninvasively localizing the site of insertion of the accessory pathway.