Accessory pathway localization by QRS polarity in children with Wolff-Parkinson-White syndrome

AP Localization by QRS Polarity in Children. Introductions: Location of the accessory pathway (AP) in Wolff-Parkinson-White (WPW) syndrome can be determined accurately by the QRS polarity on resting ECG. These ECG characteristics may be different in children, and no algorithm has yet been tested. Methods and Results: A total of 153 resting ECGs of symptomatic children with WPW syndrome were retrospectively analyzed. The anatomic AP location had been established fluoroscopically at eight possible sites during radiofrequency catheter ablation. Two independent observers predicted AP location on blinded ECGs with a QRS polarity algorithm for adults using leads II, III, aVL, V-1, and V-2. Subsequently, the QRS polarity for all individual ECG leads was evaluated and a new algorithm for children was devised. With the adult algorithm, the observers correctly predicted only 55% to 58% of AP locations. The septal and right-sided pathways often were inseparable, and mid-septal and parahisian pathways were missed. In the new children's algorithm, left lateral, left posteroseptal, and posteroseptal pathways shared a positive or intermediate QRS, polarity on V-1, with the left lateral pathway separated by a positive QRS polarity on lead III. Negative QRS polarity on lead V-1, and positive QRS polarity on lead V-3 were shared by right posteroseptal, mid-septal, parahisian, and anteroseptal pathways, with the latter two having a positive QRS polarity on lead aVF. Right lateral pathways had negative QRS polarity on lead V-1 and negative or intermediate QRS polarity on lead V-3. Overall accuracy for these five regions was 90%. Conclusion: AP characterization by QRS polarity in children with WPW syndrome is more diverse than in adults and requires other ECG leads to establish five AP regions.