Feasibility Of Percutaneous Epicardial Mapping And Ablation For Refractory Atrial Fibrillation: Insights Into Substrate And Lesion Transmurality.

BACKGROUND: Recurrences of atrial fibrillation (AF) after ablation have been attributed to conduction gaps and non-transmural ablation lesions OBJECTIVE: To assess the feasibility of adjunctive percutaneous mapping of the epicardial regions of the left atrium to characterize the transmural extent of substrate and ablation lesions.

METHODS: Between 2014-2018, combined epi-endo mapping of AF was performed in 18 patients via inferior subxiphoid percutaneous approach (16 with previously failed ablations, and 2 patients with long-standing persistent AF) at 2 centers. Epicardial substrate was compared to the endocardial electroanatomic mapping to assess transmural uniformity.

RESULTS: Amongst 18 patients, 4 demonstrated non-transmural atrial low voltage regions with relative epicardial sparing in the left atrial posterior wall. Transmural isolation of the posterior wall was achieved after an endocardial "box" lesion set in 67%, guided by epicardial voltage data, while epi-endo dissociation during AF was observed in 1 patient. In 3 patients, epicardial capture along the endocardial pulmonary vein lesion set despite endocardial capture loss and bidirectional block was observed. Two cases of mitral flutter were terminated from the epicardium. A balloon was positioned in the pericardial space in 6 patients for esophageal protection during ablation.

CONCLUSIONS: A percutaneous epicardial approach for mapping and ablation of the left atrium is feasible in the EP lab during endocardial catheter ablation for AF and may be useful as an adjunctive approach in refractory cases. High-density epicardial mapping can provide direct evidence of non-uniform lesion and substrate transmurality of the human left atrium before and after ablation.