Left atrial symmetry and volume changes after catheter ablation of atrial fibrillation

Abstract

Purpose: Atrial fibrillation (AF) is associated with electroanatomical remodeling of the left atrium (LA) with asymmetrical LA dilatation being associated with advanced AF stage. Beyond substrate progression, additional anatomical LA changes have also been described after catheter ablation. We studied the pattern of LA symmetry and volume changes after AF radiofrequency catheter ablation. Methods: We retrospectively analyzed 24 patients (mean age 62±7 years, 58% male, 71% paroxysmal AF) who were referred for circumferential pulmonary vein isolation and underwent a second procedure due to AF recurrence between 2007 and 2012 in our institution. We compared cardiac computed tomography (CT) data acquired prior to each ablation procedure. Reconstruction of the LA and the pulmonary veins (PV) was performed using specialized software (EnSite Verismo, SJM, MN). Left atrial volume (LAV) after exclusion of the atrial appendage (LAA) and the PVs was determined. The LA was then arbitrarily divided by a cutting plane between the anterior segment of the PV ostia and the atrial appendage and parallel to the posterior wall, to anterior- (LA-A) and posterior-LA (LA-P) segments. The LA-A/LAV ratio was defined as asymmetry index (ASI) and the LA-P/LA-A ratio as relative asymmetry index (ASI-r). Results: The average time between the two CT scans was 28±15 months. LAV was significantly reduced from 156±77 ml to 143±78 ml (p=0.016). In 50% of the patients there was an LAV reduction of more than 10% (10-58 ml). LA-P was reduced from 59±24 ml to 46±20 ml (p=0.001) while LA-A remained unchanged (101±57 ml to 99±61 ml, p=0.809). This resulted in a significant change in LA symmetry demonstrated by the asymmetry indexes: ASI-r was reduced from 63±19% to 51±15% (p=0.004) and ASI increased from 62±7% to 66±7% (p=0.005). LAA volume did not change significantly (9±5 ml vs. 6±10 ml, p=0.207). Conclusion: There is reverse anatomical LA remodeling despite recurring AF. While the mechanisms, i.e. reduction in AF burden or ablation-induced tissue retraction remain to be elucidated, this finding should be considered when using CT image integration of previous CT scans in patients undergoing repeat procedures.