A model study on excitation in cardiac muscle under electrical field stimulation

The authors investigated the excitation process of the cardiac muscle under electrical field stimulation using guinea pig hearts and a mathematical model. Maximum upstroke velocity of action potentials elicited by the field stimulation had a wide range of value, and its mean value was about a half as high as that from the single ventriculocytes. The phase planes of upstrokes under the field stimulation were indistinguishable from those during propagation. These results indicate that the whole cardiac tissue does not excite homogeneously, and action potential propagation does occur within the tissue. A mathematical model analysis revealed that the diverse passive membrane property of each cell was able to reproduce the inhomogeneous excitation pattern similar to that observed experimentally. It is concluded that the diverse cell membrane properties have an important role in tissue excitation under field stimulation