The continous grid model: a novel approach to improve spatial resolution and omnipolar signal reliability for electroanatomical mapping of arrhythmogenic substrates

Multipolar catheters are widely used for clinical electro-anatomical mapping to identify ablation targets. Different catheter configurations have been proposed. Grid-like catheter designs with fixed electrode arrangement allow to explore wavefront characteristics and estimate omnipolar electrograms. Yet, particularly in diseased tissue their interelectrode spacing of 4 mm often does not meet critical assumptions regarding uniformity of the unipolar signal between electrodes or the presence of a planar wavefront that are essential for accurate omnipolar signal calculations. This failure to meet the assumptions can be attributed to the spatial resolution, as the electrodes used in the omnipolar calculation may be placed in areas with tissue heterogeneity or poor electrode contact.

This study aimed to assess omnipolar signal reliability of clinically employed grid-catheters by evaluating the catheters ability to meet the assumptions of uniformity of unipolar signals between electrodes and presence of planar wavefront in each clique by analyzing three developed parameters: amplitude variability (σa), morphology variability (σm), and Non-Planarity (θ).

The Continuous Grid (C-Grid) model was developed to address issues with interelectrode spacing by spatially interpolating unipolar signals based on the originally recorded signals. This model uses amplitude, lag, and morphology as variables in an equation that allows for the computation of the unipolar signal at any point within the catheter's area. The interpolation relies on spline equations for amplitude and lag, while morphology is handled using inverse Euclidean distance. Through resampling within this model, the interelectrode distance can be virtually reduced, enhancing spatial resolution (Figure 1.A).

Two ventricular substrate maps with a total of 4,311 mapping points were studied. Results indicate that with a 4 mm interelectrode spacing of clinically employed grid-catheters, the assumptions are weakly met, showing 17.71±9.73% σa, 4.38±4.56% σm, and 22.17±25.13% θ. As the inter-electrode spacing decreases, adherence to the underlying assumptions improves, thereby enabling the computation of more reliable omnipolar signals (Figure 1.B). However, based on the C-Grid results, achieving a tolerance below 5% for the three parameters would require less than 0.5 mm spacing, which is currently a challenge to develop from the hardware perspective.

The novel C-Grid model approach allows for more accurate omnipolar signal calculations and thus, derived biomarkers. Improvement in mapping accuracy with the C-Grid model method may support more precise arrhythmogenic substrate characterization and could improve identification of ablation targets in clinical procedures.