Electrophysiological characteristics of left atrial diverticulum in patients with atrial fibrillation: Electrograms, impedance and clinical implications

Background: Left atrial diverticulum (LAD) is not rare in patients with atrial fibrillation (AF). Recent reports focused on its morphology however data on its electrophysiological characteristics are lacking. Our study aims to investigate the electrogram and impedance features of LAD. Methods: This study included 24 patients (mean age, 58.5 +/- 10.7 years) with LAD undergoing catheter ablation for AF and 24 gender-and-age-matched individuals without LAD as controls. A bipolar LAD electroanatomic map was acquired in sinus rhythm from all study participants. Points were acquired for diverticulum in the LAD group and for corresponding areas in the control group. Electrogram deflections were counted, bipolar voltage and impedance were measured for each point, and average Delta impedance and highest Delta impedance were calculated. Results: A total of 234 points were collected in the two groups. In the LAD vs. control group, median (Q1, Q3) of electrogram deflections was 6 (5, 7) and 4 (4, 5) (P < 0.0001), respectively, voltage was not significantly different (1.58 +/- 0.68 mV vs. 1.28 +/- 0.65 mV, P = 0.10), and average Delta impedance was significantly higher in the LAD group (19.5 +/- 9.0 Omega vs 3.9 +/- 1.7 Omega, P < 0.0001). A cut-off value of 9.5 Omega for Delta impedance predicted LAD with sensitivity, specificity, and positive and negative predictive values of 83.5%, 92.8%, 92.1% and 84.9%, respectively. Conclusions: Electrogram was more fractionated and impedance was higher at LAD than in corresponding areas without LAD, which might help to differentiate LAD during catheter ablation for AF. (C) 2014 Elsevier Ireland Ltd. All rights reserved.