Assessing the Stability of Complex Fractionated Atrial Electrograms for the Characterization of Atrial Substrate in Atrial Fibrillation

Aimed at characterizing the atrial substrate in atrial fibrillation (AF), a wide number of indexes has been investigated on complex fractionated atrial electrograms (CFAEs). However, many times the assessment of CFAEs signal quality as well as intra-recording and intra-patient stability of CFAEs is missing. The present work introduces the application of nonlinear metrics to assess intra-recording and intra-patient stability on a total of 204 AF bipolar CFAEs, of 16 seconds in length from patients with paroxysmal (n=15) and persistent (n=19) AF. To estimate differences between intra-recording and intra-patient CFAEs, the coefficient of variation (CV) has been used on Sample Entropy (SE) and on the Determinism (DET) of Recurrence Quantification Analysis (RQA) of the data. In addition, the variations introduced by discarding artifacted and noisy CFAE segments were also analyzed. Intra-recording analysis indicated a significant variation of CV(%) in any segment length both for DET and SE when discarding segments, with larger decreases for longer segments. Large variations of CV(%) for DET and SE at any segment length were observed in the intra-patient analysis but, in this case, discarding segments did not improve results. The Kruskal-Wallis test reported statistically significant differences for DET and SE among channels, regardless of the discarding process. Therefore, the observed high variability of CFAEs has proved that averaging data in one channel or among different channels may lead to an unfair oversimplification of CFAE-based atrial substrate characterization.