The Functional Substrate in Patients with Atrial Fibrillation is Predictive of Recurrences after Catheter Ablation.

Background Enhanced characterization of the atrial electrical substrate may lead to better comprehension of atrial fibrillation (AF) pathophysiology. Objective With the use of high-density substrate mapping, we sought to investigate the occurrence of functional electrophysiological phenomena in the left atrium and to assess potential association with arrhythmia recurrences following catheter ablation. Methods Sixty-three consecutive patients with AF referred for ablation were enrolled. Conduction abnormalities analysis relied on two acquired left atrial electro-anatomical maps (sinus and atrial paced rhythm). We classified conduction abnormalities as fixed (if these were present in both rhythms), or functional rhythm-dependent (if unmasked in one of the two rhythms). Esophagus and aorta locations were recorded to check the correspondence with abnormal conduction sites. Results 234 conduction abnormalities were detected, of which 125 (53.4%) were functional rhythm-dependent. In sinus rhythm the most frequent anatomical site of functional phenomena was the anterior wall followed by the posterior wall and in paced rhythm, the pulmonary venous antra. Sites of functional phenomena in 82.6% of cases corresponded with extra-cardiac structures such as sinus of Valsalva of ascending aorta anteriorly and the esophagus posteriorly. The vast majority (88%) of areas with functional phenomena had normal bipolar voltage. After pulmonary vein ablation, the number of residual functional phenomena is an indipendent predictor of AF recurrence (HR 2.539 [1.458 – 4.420], p-value = 0.001) with a risk of recurrences at multivariable Cox analysis. Conclusions Dual high-density mapping (during sinus and paced rhythms) is able to unmask functional, rhythm-dependent, phenomena which are predictive of AF recurrences during the follow-up.