Classifying fractionated electrograms in human atrial fibrillation using monophasic action potentials and activation mapping: Evidence for localized drivers, rate acceleration, and nonlocal signal etiologies

Abstract

BACKGROUND Complex fractionated electrograms (CFAEs) detected during substrate mapping for atrial fibrillation (AF) reflect etiologies that are difficult to separate. Without knowledge of local refractoriness and activation sequence, CFAEs may represent rapid localized activity, disorganized wave collisions, or far-field electrograms. OBJECTIVE The purpose of this study was to separate CFAE types in human AF, using monophasic action potentials (MAPs) to map local refractoriness in AF and multipolar catheters to map activation sequence. METHODS MAP and adjacent activation sequences at 124 biatrial sites were studied in 18 patients prior to AF ablation (age 57 ± 13 years, left atrial diameter 45 ± 8 mm). AF cycle length, bipolar voltage, and spectral dominant frequency were measured to characterize types of CFAE. RESULTS CFAE were observed at 91 sites, most of which showed discrete MAPs and (1) pansystolic local activity (8%); (2) CFAE after AF acceleration, often with MAP alternans (8%); or (3) nonlocal (far-field) signals (67%). A fourth CFAE pattern lacked discrete MAPs (17%), consistent with spatial disorganization. CFAE with discrete MAPs and pansystolic activation (consistent with rapid localized AF sites) had shorter cycle length (P <.05) and lower voltage (P <.05) and trended to have higher dominant frequency than other CFAE sites. Many CFAEs, particularly at the septa and coronary sinus, represented far-field signals. CONCLUSION CFAEs in human AF represent distinct functional types that may be separated using MAPs and activation sequence. In a minority of cases, CFAEs indicate localized rapid AF sites. The majority of CFAEs reflect far-field signals, AF acceleration, or disorganization. These results may help to interpret CFAE during AF substrate mapping.

Ablation of Persistent Atrial Fibrillation Targeting Low-Voltage Areas With Selective Activation Characteristics

“…CFAE signals may be caused by electrogram filtering methods or farfield potentials. 25 Relative to AF dynamics, they depend on rate and activation wavefront and may be because of passive phenomena as wave collisions, pivot points, or slow/anisotropic conduction, but also may be linked to AF perpetuation in meandering rotors. [25][26][27][28][29][30] In previous studies, ablation of continuous CFAE sites was associated with the highest impact on AF, producing AF slowing or termination at 50% of ablated continuous CFAE sites.…”

2012 HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Patient Selection, Procedural Techniques, Patient Management and Follow-up, Definitions, Endpoints, and Research Trial Design

“…These include pharmacological interventions, the use of monophasic action potentials, limiting ablation to areas of continuous electrical activity, and activation mapping of AF. 540,548,549,550,551 Unfortunately, improved outcomes with CFAE ablation in patients with persistent AF have not been uniformly reported, and the scientific basis for CFAE ablation is not universally accepted. Moreover, results from the STAR AF II trial have shown that the addition of further ablation (lines or CFAEs) to PVI increased ablation time but did not reduce the recurrence of AF in 589 patients with persistent AF.…”

Mechanisms of Atrial Fibrillation – Reentry, Rotors and Reality

“…55 Given the predominantly functional nature of CFAEs, however, this explanation seems unlikely, and Narayan's group has demonstrated that CFAEs are largely spatially unrelated to sites of rotors or other focal AF drivers. 70 Nevertheless, all CFAEs may not be equivalent, 71 and fractionation may evolve over time as AF transitions from paroxysmal to persistent. 72 Ablation of fractionated electrograms which demonstrate continuous activity or temporal activation gradients have been shown to be more strongly associated with AF slowing or termination, 73 and the subset of CFAEs that persist in AF, sinus rhythm or with atrial pacing might also be important in the pathophysiology of AF, with a potential role as an ablation target.…”