Abstract 2666: Vagal Component to Atrial Fibrillation Electrogram Characteristics in the Posterior Left Atrium in a Congestive Heart Failure Model
Introduction: Atrial fibrillation (AF) in the setting of congestive heart failure (CHF) is thought to be mechanistically dependent on conduction heterogeneity in the atrium due to fibrosis. We recently showed that vagal innervation increases with CHF, though it is not known how this contributes to AF.
Hypothesis: A vagal component to AF can be found through vagal interventions and electrogram (EGM) analysis in a canine model of CHF.
Methods: Rapid ventricular pacing was performed 7 dogs to induce CHF. After 3 weeks, epicardial mapping was performed in the posterior left atrium (PLA) and left atrial appendage (LAA). AF was induced by burst pacing first with 20 Hz vagal stimulation (VS) and then with atropine for parasympathetic blockade (PB). The EGMs recorded during AF from both interventions were measured by the following: fractional interval (FI) for fractionation, Shannon’s entropy (ShEn) for complexity, dominant frequency (DF), and organization index (OI).
Results: During VS AF, the PLA had shorter FIs (84±11 vs. 110±23 ms, p<0.008), greater ShEn (0.76±0.04 vs. 0.67±0.06, p<0.003), and lower OI (0.42±0.06 vs. 0.51±0.08, p<0.02) than the LAA. There was no difference between PLA and LAA for DF (7.8±0.8 vs. 8.1±1.0 Hz, p=NS). In the PLA, PB increased FIs from 84±11 to 111±28 ms (p=0.05) and increased OI from 0.41±0.06 to 0.49±0.05 (p<0.05). PB did not significantly change ShEn or DF in the PLA or any measure in the LAA.
Conclusions: The reduction of fractionation and increased organization with PB in the PLA, where vagal innervation is known to be more concentrated, demonstrates a likely vagal component to CHF AF. Vagal innervation in the PLA is thus an attractive therapeutic target for AF.