Interdependence of local cycle length, duty cycle, spatiotemporal consistency, and bipolar voltage in the atrial fibrillation substrate

Appropriate targets for catheter ablation of atrial fibrillation (AFib) beyond pulmonary vein isolation are still controversially discussed. Various approaches such as ablation of complex fractionated atrial electrograms (EGMs), areas with spatiotemporal dispersion, and areas with increased rotor density have not been reproducible or failed to improve clinical success rates. Local cycle length (CL) and duty cycle (DC) during AFib offer novel measures to characterize the atrial substrate.

This study aims at providing insights into the interdependence of observed CL, DC and spatiotemporal consistency as well as their correlation to bipolar voltage as established substrate parameter to improve the individual characterization of the AFib substrate and tailor ablation strategies in future.

In patients with paroxysmal or persistent AFib, a high-resolution 3D map was recorded at baseline during AFib. Intracardiac EGMs were preprocessed to improve local signal quality and far field suppression. EGMs were recorded with a multipolar, basket-shaped high-density mapping catheter. Each mapping point comprised four parameters: CL, DC, spatiotemporal consistency, and bipolar voltage amplitude. CL quantifies the time between subsequent local activations, DC quantifies the fraction of CL with local EGM activity, and consistency (cons) quantifies the spatiotemporal consistency of EGM morphology. Only mapping points with cons > 0.5 that fulfilled the general mapping criteria were analyzed. DC > 97% as well as bipolar voltage amplitudes > 1mV were excluded due to proneness to artefacts. Weighting of individual mapping points balanced out differences in the number of EGM acquisitions per patient. Orthogonal linear regression as well as correlation analysis revealed interdependencies between mapping parameters.

57 patients (20 paroxysmal / 37 persistent AFib; mean age 67 years; mean left atrial volume 219 ml; 17 female) were enrolled. A total of 1.3 million mapping points fulfilled the general mapping criteria and exceeded the consistency threshold of 0.5. The figure shows colour-coded, two-dimensional histograms for each pair of parameters. Orthogonal linear regression yielded a significant model for all pairs of mapping parameters visualized as grey line. The correlation between CL and consistency as well as between bipolar voltage and consistency was negligible. Low correlation with bipolar voltage was expected since the novel features do not include voltage in their metrics. Correlation coefficients 𝜌 with |𝜌| > 20% revealed interdependences between CL and DC, between DC and consistency, as well as between DC and bipolar voltage. See figure for detailed results.

CL and DC in combination with consistency complement bipolar voltage measurements and can help to characterise the local atrial substrate. Further research is needed to identify an ideal combination of mapping parameters and eventually adjust the individual ablation strategy.