Characterising bi-atrial mechanisms of atrial fibrillation using high density non-contact mapping

Abstract

A universal description of mechanisms of AF activation remains elusive. This thesis seeks to apply emerging techniques of global non-contact mapping to further understand mechanisms of AF activation and identify patient specific phenotypes.
Methods were developed to allow quantification of complex patterns of activation and apply signal processing tools including dominant frequency and phase analysis to characterise AF properties.
These methods were applied to analyse the impact of adenosine during AF, which is known to alter atrial electrophysiological properties. A significant shortening of atrial fibrillation cycle length, alongside an increase in dominant frequency was associated with a promotion of rotational patterns of activation throughout the left atrium.
Extended and repeated recordings were analysed to identify both the optimal time period required for mapping and the spatial consistency of complex activation. Localised irregular activation patterns characterised by wavefront pivoting, partial rotation and splitting were highly spatially stable and coincided with areas of increasing conduction heterogeneity during short coupled atrial pacing.
A technique using mean phase coherence was developed to allow analysis of interatrial propagation during simultaneous bi-atrial mapping of AF. Properties of atrial activation were identified to reveal predictors of AF termination with targeted ablation. Differences in the balance of interatrial activation could be observed between patients with changes in right atrial activation properties reflecting more arrhythmia complexity, refractory to acute termination with ablation.
A novel method was developed to attempt to further characterise individual AF phenotypes based on whole chamber patterns of AF activation. The concept of recurrence was used to calculate both whole chamber and localised measures of organisation which was shown to correlate closely with both clinical AF phenotype and predict acute AF termination with ablation.
Finally, clinical outcomes of a cohort of patients treated with a charge density guided ablation strategy are presented.
In conclusion, novel insights into the bi-atrial properties of AF activation identified with charge density non-contact mapping are presented alongside a novel technique to quantify whole chamber organisation during AF, which aims to identify AF phenotypes and predicts acute AF termination with ablation.

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Identifiers

ORCID for Michael Mahmoudi: orcid.org/0000-0003-1293-8461

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