Electrocardiographic and electrophysiologic predictors of successful ablation site in patients with manifest posteroseptal accessory pathway.

Background: Prediction of accessory pathway (AP) location before radiofrequency ablation has become increasingly important for patients with AP; this is especially true for posteroseptal (PS) APs. Objective: To identify electrocardiographic and electrophysiologic predictors of pathway location in patients with manifest posteroseptal AP. Methods: A detailed electrocardiographic analysis, electrophysiologic study, and ablation were performed in 94 patients with single manifest posteroseptal AP (mean age 35.0 ± 13.8 years; 56 males). Results: Localization was right PS in 68 patients, left PS in 19 patients, and coronary sinus and its branches in seven patients. Common to all the patients with posteroseptal AP was a negative delta in at least two inferior leads. The most sensitive and specific parameter for differentiating left posteroseptal APs from right posteroseptal APs was an R/S ratio ≥1.0 in lead V1 (sensitivity 100% and specificity 100%). The R-wave amplitude in lead I (sensitivity 54%, specificity 67%), and delta ventricularatrial interval (sensitivity 75%, specificity 87%) had much lesser sensitivity and specificity in this regard. The epicardial posteroseptal APs were discriminated from endocardial variant by the positive delta in aVR (sensitivity 71% and specificity 99%) and negative delta in II (sensitivity 100% and specificity 20%). Delta wave polarity in V1 was not helpful for differentiating right-sided from left-sided posteroseptal APs. Conclusions: This study demonstrated that in patients with posteroseptal AP, successful ablation site could be predicted to be on the right or left endocardial surface using R/S ratio in lead V1. Necessity for Coronary sinus catheterization and angiography is predictable using delta wave polarities in leads aVR and II.