Anatomical analysis of recurrent conduction after circumferential ablation

There is general agreement on the importance of electrical isolation of antral (including pulmonary vein) myocardium for effective atrial fibrillation (AF) ablation. However, isolation is often impermanent, and return of conduction (RoC) is associated with recrudescent AF. It is generally assumed that the mechanism of RoC is recovery of ablated myocardium, but this is based almost solely on experience after ablation at the venoatrial junctions. Our objective was to perform an anatomical analysis as a means to gain further insight into RoC risk factors and mechanism(s) after wide-area circumferential ablation.

Retrospective review of data from 512 consecutive patients who underwent wide-area circumferential antral ablation. After achieving left and right antral electrical isolation, each patient underwent a period of observation for RoC during this initial procedure. In addition, 76 of the 512 patients underwent a repeat procedure at an average of 10 months later, at which time they were again assayed for RoC.

Left or right antral RoC was observed in 39 (8%) or 21 (4%) patients, respectively, during the initial procedure, and 26 (34%) or 16 (21%) patients, respectively, during the repeat procedure. Left antral RoC was more commonly observed among patients manifesting a long segment separating the circumferential lesion and the venoatrial junctions, and usually occurred in this segment, often at sites distant from ablated sites. Right antral RoC commonly occurred in the anterior and superior antral regions, also often at sites that were distant from ablated sites.

In the left antrum, there was a correlation between electrophysiologic (RoC) and anatomic (long segment) properties. The observation in both antra that RoC often occurred in previously unablated areas suggested that, as an alternative to recovery of ablated myocardium, a second mechanism of RoC was plausible: conduction via unablated myocardium, which was not immediately manifest. These observations have compelled us to modify our circumferential lesion.