Unravelling the Underlying Arrhythmia Mechanism in Persistent AF – Results from the Signal Transfer of AtRiaL fIbrillation to Guide Human Treatment (STARLIGHT)

: Background: The mechanisms that initiate and sustain persistent atrial fibrillation are not well characterised. Ablation results remain significantly worse than in paroxysmal atrial fibrillation in which the mechanism is better understood and subsequent targeted therapy has been developed. The aim of this study was to characterise and quantify patterns of activation during AF using contact mapping. Methods and Results: Patients with persistent atrial fibrillation (n=14, mean age 61±8 years, LVEF 59±10%) underwent simultaneous biatrial contact mapping with 64 electrode catheters. The atrial electrograms were transformed into phase and subsequent spatiotemporal mapping was performed to identify phase singularities (PS). PS were located in both atria but we observed more PS in the left atrium compared to the right atrium (LA 779 ± 302, RA 552 ± 235, p=0.015). Although some PS of duration sufficient to complete >1 rotation were detected, the maximum PS duration was only 1150ms, and the vast majority (97%) of PS persisted for too short a period to complete a full rotation. Whilst in selected patients there was evidence of PS local clustering, overall PS were distributed globally throughout both chambers with no clear anatomical predisposition. In a subset of patients (n=7) analysis was repeated using an alternative established atrial PS mapping technique, which confirmed our initial findings. Conclusions: No sustained rotors or localized drivers were detected, and instead the mechanism of arrhythmia maintenance was consistent with the multiple wavelet hypothesis, with passive activation of short-lived rotational activity.