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(Circulation Research. 2000;86:e19.)
© 2000 American Heart Association, Inc.

Research Commentary

Influence of a Perfusing Bath on the Foot of the Cardiac Action Potential

Bradley J. Roth

From the Department of Physics, Oakland University, Rochester, Mich.

Correspondence to Brad Roth, Department of Physics, Oakland University, 190 SEB, Rochester, MI 48309. E-mail roth{at}oakland.edu

Abstract—Recently, Spach et al (Circ Res. 1998;83:1144–1164) measured the transmembrane action potential 150 to 200 µm below the tissue surface during longitudinal and transverse propagation. They found that "during longitudinal propagation there was initial slowing of V_m [action potential] foot that resulted in deviations from a simple exponential... " (p 1144). They attributed this behavior to the effects of capillaries on propagation. The purpose of this commentary is to show that the perfusing bath plays an important role in determining the time course of the action potential foot, even when the transmembrane potential is measured 150 µm below the tissue surface. Using numerical simulations based on the bidomain model, we find that the action potential foot for transverse propagation is nearly exponential (_foot=314 µs). For longitudinal propagation, the action potential foot is not exponential because of an initial slowing (best-fit _foot=483 µs). We conclude that the perfusing bath must be taken into account when interpreting data showing differences in the shape of the action potential foot with propagation direction, even if the transmembrane potential is measured 150 µm below the tissue surface. The full text of this article is available at http://www.circresaha.org.

Key Words: bidomain • action potential foot • perfusing bath • anisotropy

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