Circumferential Pacing Reveals Microstructure of Cardiac Tissue Preparations from Small Animals – An Approach to Classify Microfibrosis

Micro-obstacles like microvessels, intercellular clefts and fibrotic layers in cardiac tissue influence the propagation of an excitation wavefront and therefore may lead to arrhythmias. Detection and classification of these structures is challenging because of the small dimensions of the fibrotic inlays and their different spatial characteristics. Our hypothesis is that local recordings of extracellular signals with high spatial resolution can reveal structural properties by applying electrical stimuli around the recording site and analyzing the directional dependence of signal parameters. Myocardial preparations of 5 guinea pigs and 5 rabbits were used. A flexible miniature sensor array comprising 4 electrodes with 50 µm inter-electrode spacing was placed on the tissue preparation to record extracellular potentials. The tissue was paced at varying positions around the sensor array at twice threshold current. For analysis the signal amplitude A and the fractionation index FI (i.e. the number of deflections within the potential waveform) were computed. The evaluated parameters showed the expected directional dependence and therefore enable the classification of the directional dependence of pacing site on extracellular potentials. This could provide the basis to characterize and quantify fibrosis in cardiac tissue by means of pacing techniques and signal analysis.