Insights into electrophysiological mechanisms of atrial fibrillation propagation using simultaneous bi-atrial mapping

Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Oxford Biomedical Research Centre Introduction Early evidence of pulmonary vein triggers initiating AF has led to focus on the left atrium (LA). Little work has been done to characterise the role of the right atrium (RA) in AF maintenance. Purpose To characterise the relative roles of the LA and RA in maintenance of atrial fibrillation and explore mechanisms of AF propagation. Methods Simultaneous bi-atrial mapping was carried out in patients undergoing first time catheter ablation using 2 linked non-contact charge density mapping systems to obtain 30-second recordings during AF. The predominant channel of communication between chambers was identified and the time difference across this channel measured (see figure). The proportion of signals earlier in each chamber was calculated and a dominant chamber identified if preceding the opposite chamber for ≥60% of the recording. AF was characterised in each chamber according to frequency of specific propagation patterns (localised rotational activation (LRA) and focal firing (FF)). The difference in AF characteristics in the LA and RA according to acute procedural outcome (termination with ablation vs. DCCV) was measured using 2-way ANOVA and predictors of AF termination identified using binomial logistic regression. Results Twenty-one patients were included (16 persistent AF, 5 paroxysmal AF, 11 in sinus rhythm at baseline) with 41 maps obtained prior to ablation. A dominant chamber was identified in 11 maps (in 9 patients). Of these, 5 maps (in 4 patients) were LA dominant, and 6 maps (in 5 patients) were RA dominant. The remainder showed balanced interatrial propagation. For patients with persistent AF, in the RA, those needing DCCV had more LRA than those with termination with ablation (79 activations, (95% CI 65-93) vs. 51 (30-71); p = 0.025). There was no difference in the LA in the two groups (77 vs 59, p = 0.541). There were fewer FFs in the RA vs LA in patients needing DCCV (123 (106-140) vs. 155 (137-172), p = 0.012)(see panel F). No differences in distribution of LIA were observed. The frequency of LRA (p = 0.003) and FF (p = 0.004) in the RA, and RA AFCL (p = 0.041), were predictors of acute procedural outcome. Conclusions Our novel approach of simultaneous bi-atrial mapping revealed that mechanisms responsible for AF maintenance were evenly distributed between atria whilst acute AF termination with left atrial ablation was dependent on the contribution of right atrial substrate. Strategies incorporating right atrial mechanisms may result in improved outcomes from AF ablation. Abstract Figure.

Spatial and Temporal Variability of Rotational, Focal and Irregular Activity: Practical Implications for Mapping of Atrial Fibrillation

Background Charge density mapping of atrial fibrillation (AF) reveals dynamic patterns of localised rotational activation (LRA), irregular activation (LIA) and focal firing (FF). Their spatial stability, conduction characteristics and the optimal duration of mapping required to reveal these phenomena and has not been explored. Methods Bi-atrial mapping of AF propagation was undertaken and variability of activation patterns quantified up to a duration of 30-seconds(s). The frequency of each pattern was quantified at each vertex of the chamber over 2 separate 30s recordings prior to ablation and R2 calculated to quantify spatial stability. Regions with the highest frequency were identified at increasing time durations and compared to the result over 30s using Cohen’s kappa. Properties of regions with the most stable patterns were assessed during sinus rhythm and extrastimulus pacing. Results In twenty-one patients, 62 paired LA and RA maps were obtained. LIA was highly spatially stable with R2 between maps of 0.83(0.71-0.88) compared to 0.39(0.24-0.57) and 0.64(0.54-0.73) for LRA and FF, respectively. LIA was also most temporally stable with a kappa of >0.8 reached by 12s. LRA showed greatest variability with kappa>0.8 only after 22s. Regions of LIA were of normal voltage amplitude (1.09mv) but showed increased conduction heterogeneity during extrastimulus pacing (p=0.0480). Conclusion Irregular activation patterns characterised by changing wavefront direction are temporally and spatially stable in contrast with rotational patterns that are transient with least spatial stability. Focal activation appears of intermediate stability. Regions of LIA show increased heterogeneity following extrastimulus pacing and may represent fixed anatomical substrate.