Complex fractionated atrial electrograms (CFAEs) are commonly recorded during atrial fibrillation (AF), but their role in the pathogenesis of AF has not been clearly defined. Studies have suggested that CFAEs may represent sites necessary for maintenance and perpetuation of AF. However, CFAEs recorded during paroxysmal AF and those recorded during persistent AF may represent a different underlying phenomenon. Ciaccio and group designed a study to look at the differences between CAFÉ’s in paroxysmal and persistent AF.

Twenty patients referred to Columbia University Medical Center were included in the study. There were ten patients with paroxysmal AF and the other ten had persistent AF. All anti-arrhythmic drugs were discontinued before the study. CFAEs were defined as high frequency signals with multiple positive or negative deflections or continuous electrical activity with no obvious isoelectric baseline. CFAE recordings over 16.8 seconds in duration were obtained from two sites in each patient at each of the ostia of the pulmonary veins and from the posterior and anterior left atrial free wall. CFAE recording sites were marked on the three dimensional CARTO maps. Only signals that were identified by two electrophysiologists to be CFAEs were included in the analysis. From each recording, two consecutive 8.4-second CFAE sequences were extracted and analyzed. A total of 480 CFAE sequences were included in the analysis.

Results showed that significant differences exist in CFAE patterns, especially in those recorded at the LSPV and posterior left atrial free wall, between acutely induced and persistent AF. CFAE deflections were more non-uniform and heterogeneous during acutely induced AF in patients with clinical paroxysmal AF compared with persistent AF. The pathogenesis of persistent AF involves complex, time-varying alterations at the cellular and tissue levels. Electrogram fractionation may occur resulting in micro reentry which one would expect to cause more homogenous and repeating CFAE patterns. However, even in the absence of structural changes, CFAEs may be seen due to irregular activation patterns that are recorded in patients with paroxysmal AF, who lack structural heart disease and have sinus rhythm most of the time. Wavebreaks and changes in the direction of activation as a result of changing refractoriness in the tissue surrounding rotors may cause increasingly fractionated electrogram morphology in otherwise normal tissues which could then lead to more heterogeneous and non-repeating CFAE patterns.

Targeting CFAEs with ablation aims to remove the substrate for AF, assuming that CFAEs represent electrical phenomena associated with arrhythmogenic substrate. Modest short-term efficacy has been achieved by CAFÉ guided catheter ablation in persistent AF, but only after a second ablation procedure in about 40% of patients. Targeting CFAEs in paroxysmal AF is even less clear. If CFAEs associated with greater morphologic variability as seen in patients with paroxysmal AF represent wavebreak sites at the periphery of the sources, one would expect them to be less effective as ablation targets. In contrast, if CFAEs with low morphologic variability represent electrophysiologic phenomenon occurring within the arrhythmogenic sites, they would be more suitable targets for ablation. In either case, accurate quantification of signal morphology is a rational first step in identifying such suitable areas, and this study shows that it is feasible to do so.

Reference:

Ciaccio EJ, Biviano AB, Whang W, Gambhir A, Garan H. Different characteristics of complex fractionated atrial electrograms in acute paroxysmal versus long-standing persistent atrial fibrillation. Heart Rhythm. 2010 Sep;7(9):1207-15.