Abstract 14746: Association of Left Atrial Late Gadolinium Enhancement With Electrogram Abnormalities, Tissue Impedance, and Proximity to the Aorta

Abstract

Introduction: Left atrial (LA) late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) predominates near the aorta(AO); however, LGE does not equate fibrosis and may be artifactual or indicate expanded interstituim. Hypothesis: We sought to examine the association of LA LGE with proximity to the descending and ascending AO and use regional impedance and voltage measurements to dissect the mechanism of LGE . Methods: The retrospective cohort included consecutive patients who underwent pre-procedural CMR and atrial fibrillation (AF) ablation between January 2016 - 2021. The association of voltage amplitude, impedance, and image intensity ratio (IIR) at each electroanatomic map point with distance from the nearest AO point was examined after adjustment for age, sex, AF type, AO stenosis, LA volume, and AO diameter. Results: Included 63 patients (age 65.5±8.8 years, 33% female). Among 42 ablation naive patients, distance from AO was unassociated with bipolar and unipolar voltage amplitudes, but associated with impedance (+0.04 ohm/mm, P=0.011) and IIR (-0.03 /mm, P<0.001). Among 21 patients with prior ablation, distance from AO was unassociated with IIR, but associated with bipolar (+0.01 mV/mm, P<0.001) and unipolar (+0.01 mV/mm, P=0.001) voltage amplitudes and impedance (+0.03 ohm/mm, P=0.025). Conclusions: Given lower impedance but normal voltage, de novo peri-AO LA-LGE likely signifies expanded interstitium, rather than fibrosis or fat infiltration. Following ablation, peri-AO voltage and impedance are both decreased compared to other LA regions, suggesting that peri-AO lesion delivery is more effective, likely due to lower impedance at baseline.