In the canine epicardium, excitation spread is 2.4 times faster, tissue resistivity is 3.2 times lower, and depolarization voltage is 3 times greater parallel to cardiac fibers than perpendicular.
How does cardiac fiber orientation influence wavefront voltage, conduction velocity, and tissue resistivity in the canine epicardium?
Cardiac fiber orientation significantly affects conduction velocity, tissue resistivity, and wavefront voltage, challenging the conventional uniform double-layer current source hypothesis.
When the canine epicardium is stimulated, the spread of epicardial excitation is 2.4 times faster parallel to the long axes of the cardiac fibers than perpendicular to them. Likewise, gross tissue resistivity is lower parallel to fibers by a factor of 3.2, and the voltage across the depolarization wave is approximately three times as great in the longitudinal direction. Equations are presented which relate these variables. Theoretical considerations confirm the experimental finding that the potentials around a wave of depolarization cannot be accounted for by the conventional hypothesis that the wavefront is a uniform double-layer current source.
Roberts et al. (1979) studied Cardiac electrophysiology. Epicardial stimulation parallel to cardiac fibers vs. Stimulation perpendicular to cardiac fibers was evaluated on Spread of epicardial excitation, tissue resistivity, and voltage across depolarization wave. In the canine epicardium, excitation spread is 2.4 times faster, tissue resistivity is 3.2 times lower, and depolarization voltage is 3 times greater parallel to cardiac fibers than perpendicular.
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