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CARTO (Biosense Webster) and NavX (St Jude Medical) provide different algorithms to support Complex Fractionated Atrial Electrograms (CFAE)-guided ablation of atrial fibrillation (AF). CARTO uses the Interval Confidence Level (ICL) as its primary metric, with Average Complex Interval (ACI) and Shortest Complex Interval (SCI) as complementary metrics for CFAE identification. Similarly, NavX uses CFEmean and CFE-StdDev respectively. Differences in commercial CFAE algorithms have never been formally investigated, and furthermore no defined thresholds exist for the complementary metrics to characterize CFAE. This could potentially impact CFAE-targeted AF ablation.Methods: Bipolar electrograms (EGMs, 2.5 s duration) at different left atrial regions were collected from 18 patients undergoing first time persistent AF ablation guided by EnSite NavX: pre- (455 EGMs), and post- (342 EGMs) pulmonary vein isolation and roof line creation. The EGMs and their calculated CFEmean and CFE-StdDev were exported and analysed offline with a validated (100% agreement) MATLAB script that calculates ICL, ACI and SCI. To demonstrate the significance of threshold selection, each EGM was classified as either fractionated or non-fractionated according to both NavX (CFEmean 30-120 ms) and CARTO (using ICL ≥ 4; 5; 6; 7), as well as whether or not there was agreement (i.e. both CFAE or both non-CFAE) between the classifications. Where EGM classifications agreed (CFEmean 30-120 ms and ICL ≥ 4), their respective CFE-StdDev, ACI and SCI were selected to generate ROC curves in an attempt to optimize sensitivity and specificity for CFAE categorization based on the agreement between the two commercial systems.Results: CFEmean increased and ICL decreased post-ablation (Fig. 1A). CFAE categorisation varied according to the use of CFEmean or ICL, and for each ICL threshold (Table [1][1]). Classification agreement between ICL and CFEmean decreased from 79% to 63% as the ICL threshold increased from 4 to 7 (Fig. 1B). For CFAE discrimination, ROC analysis indicated thresholds for: CFE-StdDev at 58 ms (sensitivity: 0.892, specificity: 0.716; area under ROC curve: 0.821, p ≤ 0.0001); ACI at 85 ms (0.869; 0.681; 0.784, ≤0.0001, respectively); and SCI at 62 ms (0.876; 0.738; 0.865; ≤0.0001, respectively). | CFAE metrics & thresholds | % of EGMs categorised as CFAEs ||: |  || ICL > =4 | 58% || ICL > =5 | 51% || ICL > =6 | 44% || ICL > =7 | 36% || CFEmean (30-120 ms) | 70% |Table 1 Conclusions: Ablation reduces fractionation irrespective of whether ICL or CFEmean are used for CFAE assessment, implying that both CARTO and NavX are sensitive to similar atrial substrate electrical characteristics. However, CFAE categorisation as performed by the two systems does not always agree, which may potentially affect substrate mapping and ablation targeting. The thresholds for CFE-StdDev, ACI and SCI suggested here could be used concurrently with CFEmean and/or ICL to improve CFAE classification and potentially increase CFAE-guided ablation specificity.![Graphic][2] Figure 1(A) CFEmean and ICL pre-/ vs. post-ablation. (B) % agreement between CFAE categorisation as performed by CFEmean and ICL. (C) ROC curves for CFE-StdDev, ACI and SCI for discriminating CFAEs based on the agreement between both NavX and CARTO. [1]: #T1 [2]: /embed/inline-graphic-1.gif

66 * Investigating differences in complex fractionated atrial electrogram discrimination as performed by CARTO and NavX algorithms