Complex fractionated atrial electrograms: is this the beast to tame in atrial fibrillation?

Atrial fibrillation (AF), the most common sustained arrhythmia, represents a difficult scientific challenge and remains enigmatic even after more than one century of research. Already about a hundred years ago principles that could account for organization amidst much disorganized spatial and temporal patterns of activation were proposed to prevail in the form of reentrant activity.1,2 During the last decades experimental and clinical studies have demonstrated that despite the spatiotemporal complexity of wave propagation during AF, maintenance of the arrhythmia in many cases depends on measurable deterministic properties of fast rotors and hierarchical distribution of activation rates.3–7 However, any suggestion of organization underlying AF is met with skepticism as the proclaimed organization is quite elusive, particularly since the analysis and treatment of the arrhythmia in humans depends, for the most part, on catheter-based, relatively low resolution electroanatomical mapping.8 As such, when the isolation of pulmonary veins (PVs) by radiofrequency ablation is insufficient to eliminate AF, most clinical electrophysiologists today move on to target areas of complex electrograms, whose ever changing morphologies, inter-beat intervals and amplitudes have somehow led to the notion that such areas may harbor the sources that maintain AF. In this context, Nademanee et al,9 identified a particular class of electrograms, which he termed “complex fractionated atrial electrograms” (CFAEs), at sites outside the four PV ostia, on the posterior and anterior left atrial (LA) walls. Nademanee’s work stirred much interest among those studying AF, and since then many attempts have been made to automatically quantify CFAEs and extract from them a better understanding of AF mechanisms.10–13 The ultimate common goal is to guide ablation procedures and increase their efficacy in patients with either paroxysmal or persistent AF.9,14