Atrial fibrosis in left atrial arrhythmias: results of comparative analysis by low voltage area mapping

Abstract Introduction Atrial fibrosis plays a significant role in the development of atrial arrhythmias, both in atrial fibrillation (AF) and atypical (left) atrial flutter (AAFL). While predisposing factors for AF and AAFL somewhat overlap, the differences in the substrate are still not well known. Low voltage areas (LVA), assessed using bipolar voltage mapping, are considered a surrogate for local fibrosis. In this study, we used LVA quantification in order to compare the amount of atrial fibrosis in patients with persistent AF and AAFL. Purpose To examine whether AAFL patients would have a higher percentage of atrial fibrosis than Persistent AF patients, representing a more complex fibrotic substrate. Methods This retrospective single-center study included consecutive patients who underwent ablation for AF and AAFL using the Biosense Webster CARTO mapping system from 2023 to 2024 and had bipolar voltage maps amenable to analysis. Measurements of very low voltage (0-0.2mv), low voltage (0-0.5mv), and normal (>0.5mv) areas were made using the CARTONET's (Biosense Webster) voltage histogram. Detailed voltage analysis was performed for the entire left atrium and specifically segmented for anterior and posterior walls. Statistical comparisons were conducted using the Mann-Whitney U test. Results Twenty AF patients and twelve AAFL patients were included in the study. The mean age was 70 and 67 in the AF and AAFL groups. Rate of left atrial enlargement (moderate or higher) was 61% and 54.5%, respectively. Preserved left ventricular systolic function rate was 65% and 83%, respectively. Mean low voltage and very-low voltage areas were significantly higher in AAFL, comparing AF with 6041.66mm2 vs. 2928.25mm2 (p=0.0005) and 3299.12mm2 vs. 1163.42mm2 (p=0.0003) respectively. The percentage of low-voltage and very-low-voltage areas was 52.63% and 28.64% in the AAFL group and 24.16% and 9.33% in the AF group (p=0.0007, p=0.0001, respectively). Significantly larger low and very low-voltage areas were also measured in a separated analysis of the anterior and posterior walls. Conclusion AAFL is associated with significantly more extensive areas of atrial fibrosis, represented by left atrial LVA, compared to persistent AF. This finding may represent a more progressive atrial disease in AAFL patients, and suggest the higher involvement of additional, non-fibrotic mechanisms in persistent AF.Table 1.Measurements of low-voltage area Figure 1.Voltage Map. A – AAFL; B - AF