Catheter Ablation Targeting Complex Fractionated Atrial Electrogram in Atrial Fibrillation

Abstract

The relatively low success rates seen with pulmonary vein ablation in non-paroxysmal atrial fibrillation (AF) patients as compared to those with the paroxysmal form of the arrhythmia have prompted electrophysiologists to search for newer ablative strategies. A decade has passed since the initial description of complex fractionated atrial electrogram (CFAE) ablation aimed at targeting the electrophysiological substrate in atrial fibrillation. Despite intensive research, superiority of CFAE-based ablation over other contemporary approaches could not be demonstrated. Nevertheless, the technique has an adjunctive role to pulmonary vein ablation in non-paroxysmal AF patients. Perhaps our incomplete understanding of the complex AF pathophysiology and inadequate characterization or determination of CFAE has limited our success so far. This review aims to highlight the current challenges and future role of CFAE ablation. .

Figure 1.. Semi-automated CFAE Algorithms

The 5 different semi-automated algorithms first tagged electrograms or deflections according to their specific amplitude and timing criteria adjusted to avoid noise or far-field detections. Based on the tagged deflections, each algorithm provides a quantitative measure of CFAE that is either interval or count based. In this example, the same 2.5s AF electrogram was subjected to the different algorithm. Complex fractionated electrogram mean (CFE-m) measures the mean of time intervals between all tagged deflections. Average complex interval (ACI) refers to the average interval of tagged deflections between 70 and 500ms. Shortest complex interval (SCI) denotes the shortest interval within the sample between 70 and 500ms. Interval confidence level (ICL) refers to the number of intervals between 70 and 120ms within a 2.5s sampling period. Continuous electrical activity (CEA) is defined by the presence of 2 or more successive tagged deflections with interval <50 ms and expressed as percentage of continuous activity.

Figure 2.. Variability in CFAE Determinations with Semi-automated Algorithms

Four of the five algorithms shown in Figure 1 were applied to four different 2.5s AF electrograms of increasing fractionation (sample A to D). CFAE was defined by complex fractionated electrogram mean (CFE-m) <120ms, interval confidence level (ICL) ≥5, average complex interval (ACI) ≤100ms and continuous electrical activity (CEA) ≥75%. The result is circled when the individual algorithm deemed the electrogram to be CFAE. Full agreement is seen with sample A only. This figure is adapted from Lau et al [Reference 41, Figure 2].