Background: Catheter-based ablation of accessory pathways (AP) is a standard procedure for the treatment of Wolff-Parkinson-White (WPW) syndrome. Delta wave analysis on a 12-lead electrocardiogram (ECG) is essential for predicting ablation sites. In clinical routine, previous algorithms for analysis of AP localization have proven complex, time-consuming and not precise enough.

Objectives: The aim of our study was to retrospectively develop and prospectively validate a simple ECG-based algorithm allowing for accurate and reliable localization of APs in consecutive patients undergoing AP ablation for WPW syndrome.

Methods: A total number of 109 patients who underwent successful ablation of a single manifest AP due to WPW syndrome between 2013 and 2021 were included in our study. For the exact determination of the axis of delta waves profound analyses of patients' 12-lead ECGs as well as mathematical calculations were performed. In detail, V1 allows differentiation between right- and left-sided AP. Precordial R/S transition enables a distinction to be made between right lateral and right septal AP. The axis of the delta wave was determined using leads II, III, aVR, aVL. Our algorithm was prospectively validated during electrophysiological studies by comparing its efficacy to two established algorithms (Pambrun and Arruda).

Results: In all patients (37±18 years old, 49% female) AP ablation was successfully performed. 12-lead ECG-based prediction of accurate AP localization using the new algorithm was correct in 102 patients (94%). Overall sensitivity of our algorithm was 93%, specificity was 99%, the positive predictive value amounted to 97% and the negative predictive value was determined with 99%. Our algorithm was particularly useful to distinguish between anteroseptal (sensitivity 100%, specificity 100%), posteroseptal (sensitivity 100%, specificity 91%) and anterolateral (sensitivity 100%, specificity 100%) AP in proximity to the tricuspid valve. The accuracy, defined as the percentage of patients with an exact prediction of AP localization, was significantly greater with our new algorithm compared to the Pambrun (94% vs. 84%, p=0.049*) as well as the Arruda algorithm (94% vs. 75%, p<0.001*).

Conclusion: Our novel 12-lead ECG-based algorithm enables reliable and accurate pre-interventional ablation site determination in patients with WPW syndrome. Only two steps are necessary to locate left-sided AP and three steps to determine right-sided AP. This can be done with the help of a simple flow chart or, in perspective, with the help of an app. By considering the heart axis and the axis of the delta wave our algorithm overcomes the weaknesses of the established ones. Integration of the novel algorithm may help in treatment planning and has the potential to facilitate the ablation procedures in WPW patients.