Spatial filtering of epicardial electrograms from infarct regions : an in vitro study

Epicardial electrograms from infarct regions have multiple deflections due to the superposition of different activation wavefronts. This study aims to separate local and distant wavefronts by two-dimensional spatial highpass filtering. For that purpose, extracellular electrograms were recorded from thin (<1 mm) epicardial slices from 1-day-old canine infarcts, isolated in a superfused tissue bath and stimulated at twice threshold. Two-dimensional filter algorithms were generated for orthogonal electrode arrangements with center-to-center distances from 1 mm to 0.01 mm. Optimal separation was achieved by second order highpass spatial filtering with 0.2 mm electrode spacing. In all tested algorithms the filter performance was degraded when the distance between the recording electrodes and the tissue was greater than the inter-electrode distance.<>