Abstract 626: Left Atrial Substrate Modification Guided by Polyphasic High-frequency Potentials: Spatial Distribution of Fibrillar Myocardium Defined by Electroanatomical Mapping in Patients with Paroxysmal Atrial Fibrillation
Recent electrophysiologic studies in patients with atrial fibrillation (AF) have shown that clusters of the fibrillar myocardium (FM; atrial fibrillation nest) present higher frequencies than any surrounding tissues. We hypothesized that pulmonary vein left atrial (LA) antrums have many more FMs which perpetuate AF than elsewhere in the LA. The aim of this study was to determine the spatial distribution of FM in the LA using polyphasic high-frequency potentials and electroanatomical mapping. We performed catheter ablation in 44 patients (27 male and 17 female; age 64.4 ± 11.7 years) with paroxysmal AF. Using CARTO navigation in the LA during atrial pacing, we created the shell of whole LA with fill threshold less than 10 mm, and divided the LA into 11 segments where clusters of FM were tagged. We defined FM as polyphasic high-frequency potentials showing five or more deflections within 30 ms in a single wave, as demonstrated by a high-frequency filter setting (159 to 600 Hz). Radiofrequency energy (30 W and 55 degrees, each application 20 sec) was delivered at the location of FM using a 4 mm-tip mapping catheter until elimination of high-frequency potentials. Pulmonary vein isolation was not intended in any patients. The most common site of FM was the anterior portion of right pulmonary vein (PV) antrum (84%). Next, the anterior and posterior portions of the left PV antrum were more likely to harbor FMs (64% and 48%, respectively). In contrast, FMs were less commonly observed elsewhere in the LA (posterior portion of the right PV antrum, 20%; roof, 27%; posterior wall, 11%; mitral annulus, 7%; septum, 5%; bottom, 7%; anterior wall, 0% and LA appendage, 0%). After elimination of FM, AF was rendered noninducible in 91% of the patients; at most recent follow-up (253 ± 224 days after ablation), 82% were in sinus rhythm on 24-hour Holter ECG, and 86% were palpitation-free. No complications occurred in any patients. In patients with paroxysmal AF, FM is located predominantly at the anterior portions of the right PV antrum, followed by the left PV antrum. LA substrate modification targeting for FM is safe and effective for maintenance of sinus rhythm. Understanding of the spatial distribution of FM facilitates AF ablation.