Presence and Predictors of Atrial Low Voltage Zones in Patients with non Cardiovertable Atrial Fibrillation

Background: Interventional treatment of persistent atrial fibrillation (pAF) presents a challenge due to the lack of clear evidence on adjunctive strategies beyond pulmonary vein isolation (PVI). One promising approach is ablation of left atrial low voltage zones, which has been shown to improve outcomes in patients with pAF. However, reliable assessment of left atrial endocardial voltage requires sinus rhythm (SR). In a significant proportion of patients with persistent atrial fibrillation (pAF) however, restoration of sinus rhythm (SR) cannot be achieved. These may lead to extensive ablations such as defragmentation or empirical isolation of the posterior wall of the left atrium. This study aims to investigate the potential of unsuccessful cardioversion prior ablation as a predictor for the presence of low voltage zones (LVZ) in the left atrium.

 

Methods: This retrospective, single-centre study was conducted on 264 patients (31,8% female; age: 67±10 years; mean AF duration: 1-2 years) diagnosed with pAF who underwent catheter ablation between 01/2017 and 01/2020. All patients underwent electrical cardioversion (CV) before ablation. If restoration of SR was achieved, high-density contact mapping was performed in sinus rhythm before pulmonary vein isolation (PVI), in case of unsuccessful initial cardioversion, high-density contact mapping was performed after repeated CV followed the PVI, respectively.

 

Results: Initial cardioversion was unsuccessful in 53 out of 264 (19.7%) patients. Subsequent to pulmonary vein isolation, cardioversion was successful in 47 out of 53 (81%) patients initially considered non-cardiovertible. In 32 out of 53 (60.4%) patients who had an initial unsuccessful cardioversion, no left atrial low voltage was identified. Amongst patients who underwent a successful initial cardioversion, left atrial low voltage zones were apparent in 77 out of 211 patients (36.5%). There is no significant difference in the the presence of left atrial low voltage between patients who had initially successful and unsuccessful CV (χ²(1) = 0.178, p = 0.673, φ = 0.026). According to the ROC analysis, the success of CV does not have any predictive value for LVZ (AUC 0.511).  

 

Conclusion: Cardioversion failure before pulmonary vein isolation does not predict left atrial low-voltage zones (LVZ). PVI alone may be adequate even in patient with clinically “end stage”  non-cardiovertible atrial fibrillation. Ablation beyond pulmonary vein isolation have the potential to overtreat this specific patient group, resulting in an increase in secondary arrhythmias. These findings indicate that even single-shot devices such as balloon-based techniques may be a considerable ablation strategy in these patient cohort.