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Abstract Introduction The temporal behavior of atrial electrograms (AEGs) collected during persistent atrial fibrillation (persAF) directly affects ablative treatment outcomes. We investigated different durations of AEGs collected during persAF using recurrence quantification analysis (RQA). Methods 797 bipolar AEGs with different durations (from 0.5 s to 8 s) from 18 patients were investigated. Four RQA-based attributes were evaluated based on AEG durations: determinism (DET); recurrence rate (RR); laminarity (LAM); and diagonal lines' entropy (ENTR). The Spearman correlation (ρ) between each duration versus 8 s was calculated. AEG classification was performed following the CARTO criteria (Biosense Webster) and receiving operating characteristic (ROC) curves were created for the RQA variables. Results The RQA variables successfully discriminated the AEGs: the area under the ROC curves were as high as 0.70 for AEGs with 3.5 s or greater. Three types of AEGs were found using these variables: normal, fractionated and temporally unstable. The number of unstable AEGs decreased with longer AEG segments. Different AEG durations significantly affected the RQA variables (P<0.0001), with no statistical difference between the durations 6 s, 7 s and 8 s for DET, LAM and ENTR, and no difference between 7 s and 8 s for RR (P<0.0001). AEGs with 3 s or longer have shown ρ ≥ 80% for all variables. Conclusion The RQA variables have been shown effective in the characterization of AEGs collected during persAF with a shorter duration than current recommendations, which motivates their use for the characterization of atrial substrate during persAF ablation.
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BACKGROUND AND OBJECTIVES: Although ablation of complex fractionated atrial electrograms (CFAE) in atrial fibrillation (AF) is one of the strategies for atrial substrate modification, the mechanism behind CFAE as an electrophysiological substrate remains unclear. We investigated structural differences between CFAE sites and their matched non-CFAE sites by comparing their histopathologic characteristics in canine AF models. METHODS: Atrial electrograms of four dogs were obtained from the epicardial site. AF was induced through burst atrial pacing at 600 bpm for 30 min. CFAE sites were identified during AF according to patterns visualized on the electrograms, and their matched non-CFAE sites were selected in the adjacent region, within 5 mm of each CFAE site. Tissues were harvested from CFAE sites and their matched non-CFAE sites at various locations in both atria. Histopathologic differences were identified between CFAE and non-CFAE sites. RESULTS: A total of 24 atrial tissues (12 with CFAE, 12 with non-CFAE) were evaluated. The atrial myocardium was significantly thicker at CFAE sites (1757.5±560.5 µm) than at non-CFAE sites (1279.5±337.2 µm) (p=0.036). At CFAE sites, it was filled with a significantly larger amount of fibrotic tissue than at non-CFAE sites (22.8±6.9% versus 7.2±4.7%, p < 0.001). Results were consistent across various tissue locations. The distribution of autonomic nerve innervation was similar between CFAE and non-CFAE sites. CONCLUSION: This study provides a better understanding of histological characteristics of CFAE sites, namely a thicker wall and greater amount of fibrosis. These findings may be associated with the development of CFAE and its pathophysiological contribution to AF.