QRS POLARITY ON 12-LEAD SURFACE ECG - A CRITERION FOR THE DIFFERENTIATION OF RIGHT AND LEFT POSTEROSEPTAL ACCESSORY ATRIOVENTRICULAR PATHWAYS

In this study, we tried to disclose certain electrocardiogram (EGG) cr iteria that might be useful in the classification of posteroseptal acc essory atrioventricular pathways as right and left in patients with pr e-excitation in whom the accessory pathway localization was verified b y subsequent successful ablation. Twenty such patients with posterosep tal accessory pathways (mean age 34.9 +/- 9.8; 11 male, 9 female) were included in the study. Localization of the accessory pathway was righ t posteroseptal in 13 (65%) and left posteroseptal in 7 (35%). Common to all these 20 patients with posteroseptal accessory pathways was a Q RS polarity positive in lead L1 and negative in leads D3, aVL. In pati ents with right posteroseptal accessory pathways, QRS polarity was neg ative in lead V1 in all and positive in lead V2 in 90%. On the other h and, none of the patients with left posteroseptal accessory pathways s howed negative QRS polarity in lead V1. In conclusion, these findings strongly suggest that in patients with pre-excitation, a QRS polarity negative in lead V1 and positive in lead V2 is an important surface EC G finding that signifies right-sided localization of a posteroseptal a ccessory pathway. In cases with left posteroseptal accessory pathways, QRS polarity in leads V1 and V2 has been found to be either biphasic or positive.