Abstract 9410: A Simple and Accurate Algorithm for Localizing Accessory Pathways in Patients with Wolff-Parkinson-White Syndrome

Abstract

Introduction: Delta wave morphology reflects the ventricular attachment site of accessory pathway (AP). Electrocardiographic R/S ratio and QRS polarity also depend on the AP location. Many algorithms for localizing APs are based on the delta wave morphology, R/S ratio, and QRS polarity. However, they are slightly complicated and it is sometimes difficult to determine the delta wave morphology accurately. In this study, we propose a new and simple algorithm for accurate localization of APs using only the R/S ratio. Methods: This study consisted of 101 patients with a single anterogradely conducting AP on a 12-lead ECG. R/S ratios in leads 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 consecutive patients. This algorithm was subsequently tested in the 61 residual consecutive patients. AP locations were divided into 5 regions based on fluoroscopical anatomy. Results: The new algorithm and the validation results were shown (figure). Among 61 patients, all 37 patients with left free wall APs showed the R/S ratio in lead V1 ≥ 0.5 (sensitivity 100%, specificity 100%). Left anterior and lateral APs were associated with the R/S ratio in lead aVF ≥ 1 (sensitivity 97%, specificity 100%). If the R/S ratio in lead V1 was < 0.5 and the R/S ratio in lead V2 was ≥ 0.5, the AP location was midseptal or posteroseptal (sensitivity 100%, specificity 94%). If the R/S ratio in both leads V1 and V2 was < 0.5, it was right free wall or right anteroseptal (sensitivity 89%, specificity 100%). Right anterior, lateral, and anteroseptal APs were associated with the R/S ratio in lead aVF ≥ 1 (sensitivity 98%, specificity 93%). Overall sensitivity of this method was 93% and specificity was 99%. The positive and negative predictive values were 96% and 98%, respectively. Conclusions: This novel algorithm using only the R/S ratio in leads V1, V2 and aVF provides a simple and accurate way to identify the AP localization.