Accuracy of Different Surface Electrocardiogram Algorithms for Localization of Accessory Pathway in Comparison to Invasive Electrophysiological Localization: An Observational Study

Abstract

Introduction: Detection of accessory pathway (AP) on surface ECG in sinus rhythm helps in the diagnosis of Wolff-Parkinson-White Syndrome (WPW Syndrome), Catheter ablation of AP was indicated in symptomatic patients with preexcitation. Pre-ablation AP localization inferred from the 12-lead surface electrocardiogram (ECG) facilitates a tailored ablation strategy; there by specific risk can be properly assessed. As they are based on pre-excitation in the basal state, available algorithms can lead to complex and ambiguous analysis, mostly due to the variable influence of the AP over QRS morphology. Though various algorithms on surface ECG are available to predict the site of AP on surface ECG, but none of them are accurate. So, we have compared the accuracy of different algorithms in predicting the AP localization in comparison to electrophysiological study (EPS) diagnosis. Methodology: This retrospective observational study cohort consisted of 100 consecutive patients above 15 years of age presented to the tertiary care center with the history of palpitations or for assessment of a manifest AP. Accessory pathways were identified according to the site where successful radiofrequency energy was applied. Arruda algorithm, Milstein algorithm, Fitzpatrick algorithm and Pambrun algorithm were applied on a sinus rhythm manifest preexcited ECG to predict the AP localization by two independent investigators who are unaware of site of successful catheter ablation. Then those were compared with the EPS localization to test the accuracy of individual algorithm. Then Cohen’s Kappa was run to determine if there was agreement between any of the four different algorithms with EPS using SPSS version 20.0. Results: In the study population of 100 patients, male to female ratio of study population was 1.6:1, with a mean age of presentation 43.86 ± 11.4 years with the most common age group of 31 to 45 year. when the AP locations were categorized based on EP Study 56 percent of the AP were found on the left side while 43 percent of the AP were found on right side, 77 percent of the AP were septal pathways. Among the leftsided pathways, left anteroseptal constitutes majority followed by left posteroseptal pathway. On right side majority were in right posteroseptal location in our study. Based on 4 surface ECG algorithms AP was localized and each algorithm was compared with invasive EPS localization for accuracy using Cohen’s Kappa agreement analysis. As per agreement analysis the kappa value for Milstein, Pambrun algorithm, Fitzpatrik and Arruda were 0.188, 0.343, 0.441, and 0.645 respectively. It was found that Arruda algorithm had moderate strength of agreement with the findings of EPS (κ = 0.645). This is the proportion of agreement over and above chance agreement and which was statistically significant and the strongest among all the four algorithms. Conclusion: Our study has compared the accuracy of 4 surface ECG algorithms in predicting the accessory pathway localization with the EPS; it has demonstrated that the Arruda algorithm is more precise and accurate among the available algorithms followed by Fitzpatrik, Pambrun algorithm and Milstein algorithm, Knowing the pathway prior to ablation allows for optimal procedure preparation, mapping pathways that are difficult to find and finally may lessen the catheter-related injury and shortens the procedural time.