Electrophysiological Characteristics of Atrial Fibrillation Trigger Sites During Ongoing Atrial Fibrillation Using Ultra-High-Resolution Mapping.

Introduction: Atrial fibrillation (AF) triggers are commonly identified at the onset of AF, but the electrophysiological behavior of trigger sites during ongoing AF remains incompletely understood. This study aimed to characterize local electrogram properties at AF trigger sites during ongoing AF using an ultra-high-resolution mapping system. Methods and Results: We retrospectively studied 45 consecutive patients with pulmonary vein (PV) or superior vena cava (SVC) triggers who underwent mapping during ongoing AF. The local cycle length (L-CL) and the proportion of the activation duration within the L-CL (duty cycle, DC) were assessed using an automated mapping tool (Ockham, Boston Scientific) and were compared among trigger veins, non-trigger PVs, the left atrium (LA), non-trigger SVC, and the right atrium (RA). A total of 56 AF triggers were documented. Trigger veins exhibited a significantly shorter minimum L-CL than the non-trigger PVs, LA, non-trigger SVC, and RA (median, 119, 129, 131, 157, and 139 ms, respectively; Conclusion: AF trigger sites were characterized by a markedly shorter minimum L-CL during ongoing AF, suggesting transient rapid activity. These findings provide mechanistic insights into the electrophysiological behavior of AF trigger sites and may offer complementary information when conventional trigger mapping is inconclusive.