Utility of a Novel 12-Lead ECG Criterion for Localizing Manifest Right Sided Accessory Pathways: A Derivation Study.

Abstract

Introduction: Most of the existing algorithms for manifest accessory pathway (AP) localization fall short in the diagnostic accuracy of distinguishing different pathway locations, particularly in the septal region. Objective and Methods: This study aims at testing an ECG criterion, the PR/QRS ratio for differentiating manifest right septal APs from the right free wall APs. PR interval, QRS width and PR/QRS ratio were measured in the most pre-excited lead. AP location was determined in LAO 45degree. Septal locations: from 12 to 6 O'clock including right anterior at 12 O'clock, right anteroseptal between 12 and 3 O'clock, right mid-septal at 3 O'clock, right posteroseptal between 3 and 6 O'clock and right posterior at 6 O'clock. Free wall locations: extending between 6 and 12 O'clock including right posterolateral between 6 and 9 O'clock, right lateral at 9 O'clock and right anterolateral between 9 and 12 O'clock. Result(s): Among 89 patients, a higher 100*PR/QRS ratio was observed in the septal wall group when compared to the free wall APs group (77.86 +/- 0.91 vs. 64.95 +/- 2.07 < 0.001). Compared to PR interval and QRS duration, PR/QRS ratio had the best predictive performance with the highest accuracy (88.8%) and the largest area under the ROC curve (0.878) with a sensitivity of 93.8%, specificity of 75% and PPV of 91%. Conclusion(s): The PR/QRS ratio is a simple yet powerful tool in localizing right sided accessory pathways that can potentially improve preprocedural counseling. However, this single-center derivation study should be considered hypothesis-generating and requires external validation. Copyright © 2026 The Author(s). Journal of Arrhythmia published by John Wiley & Sons Australia, Ltd on behalf of Japanese Heart Rhythm Society.