16-24: Identification of Heterogeneous Intra-Atrial Conduction Delay in Paroxysmal AF Patients by Dynamic Electrophysiological Characterization

Purpose of the Study: Although atrial fibrillation (AF) is classified by arrhythmia duration, the presentation, clinical course and response to treatment vary widely within paroxysmal AF (PAF) patients. We hypothesized that variable electrical remodeling exists between PAF patients, resulting in intra-atrial conduction delay which could be identified using a novel programmed stimulation technique.

Methods Used: In 15 PAF patients undergoing index PVI, high density LA contact mapping using a 20 pole Pentaray catheter was performed during pacing from two atrial sites (BCL 470ms, S1S2 350ms to atrial ERP in -2% steps). Regional atrial conduction delay (S1S2delay), activation dispersion, and AF vulnerability were measured. Computer modeling was used to interrogate the mechanism of conduction delay.

Summary of Results: Conduction delay showed a bimodal distribution (peaks for HRA / CS pacing 275 ± 11 / 271 ± 11ms and 326 ± 13 / 319 ± 16ms) and patients with inducible AF were characterized by increased activation dispersion (ΔLAT 672 ± 41ms vs 542 ± 17ms, P = 0.0446, Fig). Action potential remodeling across the population could explain observed variation in conduction delay, but resulted in insufficient conduction velocity restitution variation (3.7 ± 0.5ms-1/s vs 2.3 ± 0.5 ms-1/s, P = 0.1926) to explain the activation dispersion seen in AF-inducible patients.

Conclusions: Within the single clinical entity of PAF, programmed stimulation can identify a spectrum of activation patterns correlating with AF vulnerability. Rapid patient-specific conduction characterization may identify patients likely to respond to PVI alone for PAF.

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