Clinical mapping array with an electrode arrangement less impervious to wavefront direction: the power of the perpendicular bipole
K De Silva, S Masse, T Subha, Y Abderrahman, L Botz, G Malki, J Asta, G Mokhtar-Sasani, B Ebrahimi, D Highsmith, P F H Lai, K NanthakumarAbstract
Introduction
The traditional bipolar electrogram with bipoles sampling the electrical field in plane (parallel) to the myocardium presents a fundamental electrophysiological dilemma of electrogram dependence on wavefront directionality. Wave direction independent and travelling wave assumption free assessment of wavefront activation, especially at myocardial scar and lines of block, in a clinically deployable catheter solution with variable electrode arrangements has not been achieved.
Objective
We hypothesised that a perpendicular bipolar electrode with a contact electrode sampling myocardial activation with a non-contact floating electrode would be less dependent on wavefront direction than a traditional bipolar electrogram.
Methods
We performed experiments in Langendorff beating swine hearts (n=5) modified to permit ex-vivo Carto3 mapping. Mapping was performed on the epicardial surface with a novel array catheter (1) which consists of bipolar electrodes in plane to the myocardium (0.1mm "ultra close" (UCB) and 2mm inter-electrode spacing) and "perpendicular" (0.3mm spacing) (Perp_B). A custom pacing template was fitted over the novel array so that epicardial bipolar pacing could be performed from the East (0 degrees), North (90 degrees), West (180 degrees) and West (270 degrees). Here, pacing from 0 and 180 degrees was designed to create a wavefront across the contact electrodes (theoretically obscuring the bipolar electrogram). Directional variation was summarized using median and interquartile ranges. To compare directional sensitivity independent of absolute signal amplitude, Vpp values were normalized to the maximum within each electrode configuration and expressed as the percentage by which each direction fell short of the maximum response.
Results
In the experimental model, the unipolar electrogram peak to peak voltage (Vpp) was stable despite wavefront direction in the experimental model (2A and 2B). In contrast, the UCB, 2mm and Perp_B bipoles all exhibited change in Vpp depending on direction of pacing. When the Vpp was normalized, directional variability was highest for the UCB and 2mm bipoles and less so for the Perp_B (2C).
Conclusion
The perpendicular electrode arrangement deployed within a clinical mapping array has produced a measurable electrogram less impervious to wavefront directionality, with important implications for electroanatomic mapping and interpretation.