Utility of a Novel 12‐Lead <scp>ECG</scp> 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 45°. 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. Results 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 &lt; 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 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.