Histogram Analysis: A Novel Method to Detect and Differentiate Fractionated Electrograms During Atrial Fibrillation

INTRODUCTION: Complex fractionated atrial electrograms (CFAEs) might identify the critical substrate maintaining AF. We developed a method based upon histogram analysis of interpeak intervals (IPIs) to automatically quantify fractionation and differentiate between subtypes of CFAEs. METHODS: Two experts classified 1,681 fibrillatory electrograms recorded in 13 patients with persistent AF into 3 categories (gold standard): normal electrograms, discontinuous CFAEs, or continuous CFAEs. Histogram analysis of IPI was performed to calculate the P5, P50, P95, and the mean of IPIs, in addition to the total number of IPI (N(Total)), and the number of IPI within predetermined ranges: 10-60 (N(Short)), 60-120 (N(Intermediate)), and >120 ms (N(Long)). RESULTS: P50 and N(Long) were higher in the normal electrograms compared to the other 2 categories (P < 0.001). N(Intermediate) was higher in the discontinuous CFAE category compared to the other 2 categories. P95, mean IPI, N(Total), and N(Short) were all significantly different among the 3 categories (P < 0.001) and correlated with the degree of fractionation (r =-0.52, -0.55, 0.68, and 0.67, respectively). Receiver operating characteristic (ROC) curves showed good diagnostic accuracy (area under curve, AUC > 0.8) of P50 and N(Long) to detect normal electrograms. An algorithm using N(Intermediate) showed good diagnostic accuracy (AUC > 0.7) to detect discontinuous CFAEs, whereas P95, mean, N(Total), and N(Short) all revealed high diagnostic accuracy (AUC > 0.85) to detect continuous CFAEs. This was confirmed in a prospective data set. CONCLUSIONS: Histogram analysis of IPI can differentiate between normal electrograms, discontinuous and continuous fractionated electrograms. This method might be used to standardize and optimize ablation strategies in AF.