Effect of pulmonary vein isolation on the distribution of complex fractionated electrograms in humans

Background

Targeting of complex fractionated electrograms (CFEs) has been used as an adjunctive strategy to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF). However, it is unclear whether CFEs should be targeted before or after PVI.

Objectives

The purpose of this study was to examine the effect of PVI on CFE distribution in humans.

Methods

We compared left atrial (LA) CFE maps acquired using the NavX system before and after PVI in patients with persistent AF. CFE maps were constructed from bipolar electrograms acquired from a circular mapping catheter. At each point, the mean AF cycle length (CL) was calculated automatically by averaging the intervals between deflections over a 4-second window. Sites with mean CL ≤120 ms were considered CFE+.

Results

A total of 22 consecutive patients (82% male, age 58 ± 9 years) were studied. At baseline, 47% of the LA was encompassed by electrograms with CL <120 ms. PVI had a significant effect on CFE characteristics, with an increase in mean LA AF CL (144 ms pre-PVI vs. 214 ms post-PVI; P <.01) and a decrease in CFE+ LA surface area (47% vs 23%; P <.01). There was significant reduction in CFE burden after PVI in both PV (50% vs. 6%; P <.01) and non-PV (61% vs. 39%; P <.01) regions.

Conclusions

In patients with persistent AF, PVI results in a significant decrease in both PV and non-PV areas of CFE. To limit extensive LA ablation, PVI should be performed before targeting CFE when a combined approach is pursued.

Introduction

Over the past decade, catheter ablation therapy has assumed an increasingly important role in the treatment of patients with atrial fibrillation (AF). While pulmonary vein isolation (PVI) remains the mainstay of most catheter ablation techniques, the success rate with PVI alone has been suboptimal for patients with persistent AF (22%–75%).1, 2 Atrial substrate modification, by targeting complex fractionated electrograms (CFEs), has been described as a novel approach to AF ablation. In its original description by Nademanee and colleagues,3, 4 this technique has been performed as a stand-alone procedure for patients with paroxysmal or persistent atrial AF. More recently, targeting of CFEs has been described as an adjunct to PVI for patients with long-lasting persistent AF.⁵

The limitation of such an approach is that not all CFEs represent true drivers of AF and that these CFE areas are often widely distributed throughout the left atrium (LA).6, 7, 8 We recently demonstrated that in patients with persistent AF, areas of CFE measured with a commercially available software algorithm can encompass nearly 38% of the LA surface area.⁶ Ablation of all CFEs can therefore require an extensive amount of ablation⁹ that may increase complications and reduce LA function after ablation. It is also unclear whether CFEs should be targeted before or after PVI when a hybrid approach is pursued. While some investigators have described CFE ablation before PVI,¹⁰ others have targeted CFEs after PVI.11, 12 We hypothesized that PVI, by removing PV firing and wavefront collision at the PV/LA junction, would reduce the area of the LA encompassed by CFEs and therefore reduce the amount of radiofrequency (RF) ablation required when targeting CFEs as part of a hybrid ablation strategy.