Depolarization Diffusion During Weak Suprathreshold Stimulation of Cardiac Tissue
CASE WESTERN RESERVE UNIV CLEVELAND OHDEPT OF BIOMEDICAL ENGINEERING
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Methods For the experiments we used fluorescence optical imaging to map virtual electrode polarization at the epicardium of Langendorff-perfused rabbit hearts stained with voltage-sensitive dyes. Unipolar cathodal pacing was applied during diastole via a platinum-iridium electrodes, Results During near-threshold cathodal make stimulation we found deviations from Wikswos theory. We observed that after quick virtual electrode polarization activation starts at hyperpolarized regions and then causes a subsequent activation of the depolarized regions. Such an activation pattern appears similar to break activation. The effect of the depolarization diffusion from depolarized to hyperpolarized regions of the VE obtained by us experimentally was confirmed theoretically by 2D active bidomain simulations. Conclusions For weak near-threshold stimuli the activation pattern does not fit completely into the established model of Roth and Wikswo thus revealing its limitations.
- Medicine and Medical Research
- Anatomy and Physiology