AN ACCURATE STEPWISE ELECTROCARDIOGRAPHIC ALGORITHM FOR LOCALIZATION OF ACCESSORY PATHWAYS IN PATIENTS WITH WOLFF-PARKINSON-WHITE SYNDROME FROM A COMPREHENSIVE ANALYSIS OF DELTA-WAVES AND R S RATIO DURING SINUS RHYTHM/

Prediction of accessory pathway location before radiofrequency ablatio n has become increasingly important for patients with Wolff-Parkinson- White syndrome. However, existing electrocardiographic (ECG) criteria for localization of accessory pathways have several limitations, and t he polarity of delta waves has not been well defined. In the present s tudy, 369 patients with a single anterogradely conducting accessory pa thway who underwent successful radiofrequency ablation were included. The polarity of delta waves was defined and categorized in detail, and various ECG characteristics of the most preexcited QRS complexes were examined and compared with QRS complexes after successful ablation in the initial 182 patients, which included morphology and polarity of d elta waves, initial 20, 40, and 60 ms segments of the preexcited QRS c omplex, R/S ratio in the precordial leads, R/S ratio in the frontal le ads, delta wave axis in the frontal plane, polarity of delta waves in the frontal leads, and polarity of delta waves in the precordial leads . The polarity of the initial 40 ms segment of the most preexcited QRS complexes in each of the frontal leads, and the polarity of the initi al 60 ms segment of the most preexcited QRS complex in each of the pre cordial leads proved to be representatives of delta wave polarity in t he respective leads. The most discriminative characteristics were comb ined to form the following algorithm: step 1, analysis of R/S ratio in V-2; step 2, existence of positive delta wave in lead III (initial 40 ms); step 3, existence of positive or negative delta waves in V-1 (in itial 60 ms); and step 4, delta wave polarity in aVF or analysis of R/ S ratio in V-1. The new algorithm is featured by its easiness to be ap plied because only 4 ECG leads and 4 steps are required, and the same ECG characteristic is used in the same step in both arms of the algori thm. Together with 3 other criteria (those of Arruda, Fitzpatrick, and Xie), it was prospectively evaluated in 187 subsequent patients, and it turned out to be more accurate (93%) than other algorithms (86%, 86 %, 85%, respectively; all p values <0.05). We conclude that this new a lgorithm, through a comprehensive analysis of delta waves and an R/S r atio in a large group of patients, offers an accurate criterion for pr edicting accessory pathway location.