Electrogram Transition Patterns During Atrial Antitachycardia Pacing-Mediated Termination.

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, 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.