Precordial reverse pattern break on ECG: could it be a discriminator endo/epicardial ablation site of left posteroseptal accessory pathways

Abstract Funding Acknowledgements Type of funding sources: None. Backrounds The posteroseptal (PS) region may pose difficulty in WPW ablation due to its complex anatomical structure. The posteroseptal region may require the need for a transeptal puncture, CS venogram or coronary angiography due to its right and left endocardial and epicardial proximity. ECG prediction may prevent unnecessary procedures. Negative V1 double QRS transition pattern in the precordial leads is highly specific and validated for a right endocardial AP Purpose To investigate the presence of a reverse pattern break in the left posteroseptal [V1 (+) V3 (+)] WPW patient and compare between endocardial-epicardial ablation localization. Methods We retrospectively included 338 WPW patients into the study. 97 of them successfully ablated with posteroseptal area. Results Thirty-two of the total PS patient (33%) patients had a reverse pattern break or double transition pattern. A total of 4 patients with the middle cardiac vein (MCV) and diverticulum origin were identified. The left pattern break predicts endocardial localization 75% of the time while the right pattern predicts it 95% of the time. Conclusion Double transition and reverse pattern break are common in posteroseptal AP’s ECG. Left reverse pattern break is also highly predictive of endocardial ablation, similar to the right.