Electrogram Transition Patterns During Atrial Antitachycardia Pacing‐Mediated Termination

ABSTRACT Background Atrial antitachycardia pacing (aATP) reduces atrial tachyarrhythmia (ATA) burden, yet the electrogram dynamics after aATP delivery remain uncharacterized. We sought to characterize electrogram transition patterns during aATP‐mediated ATA termination by clinician review of intracardiac electrograms. Methods We performed a multicenter retrospective study of patients with dual‐chamber cardiac implantable electronic devices with aATP activated. Stored intracardiac atrial electrograms from aATP‐terminated ATA episodes were analyzed by electrophysiologists using predefined criteria to classify pre‐aATP electrogram regularity and post‐aATP transition patterns. Results Among 119 patients with aATP activated, 83 had device‐detected ATAs. Stored electrograms were available in 38 patients (1641 aATP‐terminated episodes), of whom 15 had prior catheter ablation for ATAs and 23 had no prior ablation. We identified six electrogram transition patterns. Regardless of pre‐aATP regularity, irregular post‐aATP activity was the most common pattern preceding termination (47% in regular and 63% in irregular pre‐aATP episodes, p < 0.001). Episodes with irregular pre‐aATP activity took longer to terminate than those with regular pre‐aATP activity (median 13 vs. 9 s, p < 0.001). At the episode level, the regular‐to‐irregular pattern was more common in patients with prior ATA catheter ablation than those without (39% vs. 22%, p < 0.001), although this was not significant after accounting for within‐patient clustering ( p = 0.11). Conclusions Regardless of pre‐aATP electrogram regularity, irregular post‐aATP activity was the most common pattern preceding termination. This association is consistent with pacing‐induced destabilization, although alternative explanations cannot be excluded. Episodes with irregular pre‐aATP activity took longer to terminate, suggesting that pre‐aATP regularity is associated with the electrogram dynamics preceding termination.