Spatial autocorrelation dimension as a potential determinant for the temporal persistence of human atrial and ventricular fibrillation.

Background: Despite being central to atrial fibrillation (AF) and ventricular fibrillation (VF) mechanisms and therapy, the factors governing AF and VF termination are poorly understood. It has been noted that system size (L) and the two-point spatial correlation length (ξ2) link to time until termination in some spatiotemporally chaotic systems, but the relationship between these determinants has not been studied in spontaneously terminating AF/VF. Objective: We assess whether the time to cardiac fibrillation termination can be predicted using a newly developed metric referred to as the spatial autocorrelation dimension (Di), given by the ratio of L and ξ2, in human AF/VF. Methods: Di was computed and compared in a multi-centre, multi-system study with data for sustained versus spontaneously terminating human AF/VF. VF data was collected during coronary-bypass surgery; AF data during clinically indicated AF ablation. We analyzed: i) VF mapped using a 256-electrode epicardial sock (n=12pts); ii) AF mapped using a 64-electrode constellation basket-catheter (n=15pts); iii) AF mapped using a 16-electrode HD-grid catheter (n=42pts). To investigate temporal fibrillation persistence, the response of AF-episodes to flecainide (n=7pts) was also studied. Results: Spontaneously terminating fibrillation demonstrated a lower Di (P<0.001 all systems). Lower Di was also seen in paroxysmal compared to persistent AF (P=0.002). Post-flecainide, Di decreased over time (P<0.001). Lower Di was also associated with longer-lasting episodes of AF/VF (R2>0.90, P<0.05 in all cases). Using k-means clustering, two distinct clusters and their centroids were identified i) a cluster of spontaneously terminating episodes, and ii) a cluster of sustained epochs. Conclusion: Lower Di correlates with less temporally persistent cardiac fibrillation. This finding provides potentially important insights into a possible common pathway to termination and therapeutic approaches. ### Competing Interest Statement The authors have declared no competing interest.