A Simple and Accurate Algorithm for Localizing Accessory Pathways in Patients with Wolff-Parkinson-White Syndrome

Introduction: A new and simple algorithm is proposed for localizing accessory pathways (APs) using only the R/S ratio. Methods: This study consisted of 101 patients with a single anterogradely conducting AP on 12-lead ECG. R/S ratios in V1, V2 and aVF were analyzed. A new algorithm was developed by correlating the 12-lead ECG findings with successful ablation sites in the 40 initial patients. This algorithm was subsequently tested in the 61 residual patients. Results: Among 61 patients, all 37 patients with left free wall APs showed the R/S ratio in V1 ≥0.5 (sensitivity 100%). Left anterior and lateral APs were associated with the R/S ratio in aVF ≥1 (sensitivity 97%). If the R/S ratio in V1 was <0.5 and the R/S ratio in V2 was ≥0.5, the AP location was midseptal or posteroseptal (sensitivity 100%). If the R/S ratio in both V1 and V2 was <0.5, it was right free wall or right anteroseptal (sensitivity 89%). Right anterior, lateral, and anteroseptal APs were associated with the R/S ratio in aVF ≥1 (sensitivity 98%). Overall sensitivity was 93% and specificity was 99%. Conclusions: This novel algorithm using only the R/S ratio provides a simple and accurate way to identify the AP localization.