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

Abstract 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 ∆impedance and highest ∆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 ∆impedance was significantly higher in the LAD group (19.5 ± 9.0 Ω vs 3.9 ± 1.7 Ω, P < 0.0001). A cut-off value of 9.5 Ω for ∆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.