Functional nature of electrogram fractionation demonstrated by left atrial high-density mapping

Area of Science:

• Electrophysiology
• Cardiac Mapping
• Atrial Fibrillation Research

Background:

• Complex fractionated atrial electrograms (CFAE) are key targets for atrial fibrillation (AF) ablation.
• Understanding the factors influencing CFAE is crucial for improving ablation strategies.

Purpose of the Study:

• To investigate the impact of activation direction and rate on electrogram (EGM) fractionation during various cardiac rhythms.
• To determine the underlying mechanisms of EGM fractionation and its relationship to structural changes.

Main Methods:

• High-density, 3-dimensional left-atrial mapping in 18 patients (9 persistent AF) during AF, sinus rhythm (SR), and coronary sinus pacing (CSp).
• Analysis of voltage, activation, and propagation maps to assess EGM characteristics and distribution.
• Correlation of CFAE sites between different rhythms.

Main Results:

• A minority of continuous CFAE sites showed fractionation in SR (15%) and CSp (12%), with poor correlation between rhythms.
• Wave collision (71%) and slow conduction (24%) were primary causes of EGM fractionation in SR and CSp.
• EGM voltage was lower during AF than SR/CSp, but higher at CFAE sites during AF.
• Lower global left atrial voltage in persistent AF compared to paroxysmal AF.

Conclusions:

• Fractionated EGMs exhibit variable distribution influenced by activation dynamics (rate and direction).
• Fractionation during SR and CSp primarily results from wave collision, not structural abnormalities.
• The absence of scar at CFAE sites in SR suggests many fractionated EGMs are functional and dynamic.