Abstract 2621: Mechanisms of CFAE Formation in the Posterior Left Atrium During Induced Atrial Fibrillation in Humans
Introduction: Complex fractionated atrial electrograms (CFAEs) are of interest to ablation of atrial fibrillation (AF). We hypothesized that CFAEs formation in the posterior left atrium (PLA) during AF is rate-dependent and secondary to fibrillatory conduction of waves emerging from drifting high-frequency sources (rotors).
Methods: In 22 pts, we induced sustained AF by burst pacing from a randomly selected pulmonary vein (PV). We recorded bipolar signals from the PLA (high density spiral catheter), right atrium and coronary sinus following AF induction (5 min) and after adenosine infusion. We analyzed transitions between organized patterns (OPs) with uniform activation sequences and changes in electrogram (EGM) morphology leading to CFAEs (duration, double EGMs and spikes number), in relation to cycle length and dominant frequency. Computer simulations of rotors in tissue with ionic current gradients helped in the interpretation of results.
Results: OPs were recorded 31% of the time. In 47% of OPs, the EGMs and PLA activation sequence were similar to those of incoming waves during PV stimulation that induced AF. Transitions to CFAEs were preceded by significant CL shortening (R2=0.94). Similarly, adenosine infusion during OPs patterns caused significant CL shortening leading to CFAEs formation. Paired analysis showed that, CFAEs were preceded by increases in the number of double EGMs, the number of spikes and the EGM duration. Activation maps during transition from OPs to fragmentation showed areas of slowed conduction and unidirectional block at bipoles with CFAEs. Seven maps showed incoming wave patterns, with the earliest activation located close to the highest dominant frequency site. Simulations predicted that:
CFAEs may form when the core of a drifting rotor approaches the recording bipole;
CL abbreviation that precedes CFAEs formation may result from a Doppler effect on the wavefronts preceding the approaching core or by acceleration of a meandering or stationary, remotely located source.
Conclusions: During induced AF, wavefront acceleration ahead of drifting rotors on the PLA results in intermittent formation of local CFAEs. Fibrillatory conduction at the periphery of a stationary or meandering rotors may also result in CFAEs.