Background: Challenges associated with PVI and lesion formation play a large role in recurrent AF after catheter ablation. Posterior wall triggers are commonly responsible for drug-refractory atrial fibrillation (AF).
Objective: Use of high-resolution percutaneous epicardial mapping to demonstrate an important mechanism of incomplete isolation of posterior wall in symptomatic recurrent AF.
Results: A 43-year-old woman with symptomatic AF refractory to dronedarone and flecainide therapy. underwent PVI x2 and cavotricuspid isthmus ablation. One year later, she remained symptomatic and was started on sotalol and dofetilide with persistent symptoms. Loop interrogation revealed increasing AF burden. She underwent repeat AF ablation with adjunctive percutaneous epicardial mapping. LA endocardial mapping showed an incompletely isolated posterior wall with sudden discontinuous focal activation. Mapping of the epicardial aspect of the posterior wall showed continuous activation during CS pacing from the floor to the right superior pulmonary vein through the epicardial septopulmonary bundle of the posterior wall. Ablation was performed from endocardial surface guided by the epicardial activation with subsequent epicardial posterior wall isolation. (Figure Below)
Conclusion: To the best of our knowledge, these are the first recordings of epicardial septopulmonary bundle activation into the posterior wall that provides direct evidence for the mechanism of failure to achieve transmural isolation of the posterior wall.