Intra-Atrial Conduction Delay Revealed by Multisite Incremental Atrial Pacing is an Independent Marker of Remodeling in Human Atrial Fibrillation

Abstract

ObjectivesThis study sought to characterize direction-dependent and coupling interval–dependent changes in left atrial conduction and electrogram morphology in uniformly classified patients with paroxysmal atrial fibrillation (AF) and normal bipolar voltage mapping.BackgroundAlthough AF classifications are based on arrhythmia duration, the clinical course, and treatment response vary between patients within these groups. Electrophysiological mechanisms responsible for this variability are incompletely described.MethodsIntracardiac contact mapping during incremental atrial pacing was used to characterize atrial conduction, activation dispersion, and electrogram morphology in 15 consecutive paroxysmal AF patients undergoing first-time pulmonary vein isolation. Outcome measures were vulnerability to AF induction at electrophysiology study and 2-year follow-up for arrhythmia recurrence.ResultsConduction delay showed a bimodal distribution, occurring at either long (high right atrium pacing: 326 ± 13 ms; coronary sinus pacing: 319 ± 16 ms) or short (high right atrium pacing: 275 ± 11 ms; coronary sinus pacing: 271 ± 11 ms) extrastimulus coupling intervals. Arrhythmia recurrence was found only in patients with conduction delay at long extrastimulus coupling intervals, and patients with inducible AF were characterized by increased activation dispersion (activation dispersion time: 168 ± 29 ms vs. 136 ± 11 ms). Electrogram voltage and duration varied throughout the left atrium, between patients, and with pacing site but were not correlated with AF vulnerability or arrhythmia recurrence.ConclusionsWithin the single clinical entity of paroxysmal AF, incremental atrial pacing identified a spectrum of activation patterns correlating with AF vulnerability and arrhythmia recurrence. In contrast, electrogram morphology (characterized by electrogram voltage and duration) was highly variable and not associated with AF vulnerability or recurrence. An improved understanding of the electrical phenotype in AF could lead to improved mechanistic classifications.

The effect of activation rate on left atrial bipolar voltage in patients with paroxysmal atrial fibrillation

“…The mid CS was chosen to ensure that the LA activated uniformly. Previous studies have shown discrepancies between LA voltage under HRA and CS pacing conditions, 30 potentially due to fusion of LA activation via the septum and Bachman's bundle. Whether different voltage-rate effects would be revealed by alternative activation vectors is not answered by these data but is worthy of further study, particularly given the lack of relationship between LA voltage in sinus rhythm and AF (where multiple, chaotic activation vectors are likely to be present).…”

Left atrial voltage mapping: defining and targeting the atrial fibrillation substrate

“…Direction-dependent effects were previously demonstrated for much larger ventricular signals [15] but have also recently been demonstrated by comparing sinus rhythm/high right atrial pacing to coronary sinus pacing in the atrium. In contrast to predictions from simulated data, these effects are highly variable indicating that voltage change could not be used, for example, to infer activation direction [16].…”

Intra- and interatrial conduction abnormalities: hemodynamic and arrhythmic significance

“…Using high-density contact mapping, Sonoda et al found that LA activation time was longer in patients with persistent compared to paroxysmal AF, despite homogeneous activation patterns in both groups [2]. Interestingly, a recent study [32] suggested that, in patients undergoing paroxysmal AF ablation, decremental conduction properties in the LA predicted a higher risk of AF recurrence during a 2-year follow-up; the association was not statistically significant. In conclusion, these measures may help assess the vulnerability of atrial tissue to AF, but evidence is insufficient for clinical applications.…”