High resolution magnetic images of planar wave fronts reveal bidomain properties of cardiac tissue

¹ Vanderbilt University

^* To whom correspondence should be addressed. E-mail: f.baudenbacher{at}vanderbilt.edu.

Submitted on July 8, 2004
Revised on August 9, 2004
Accepted on 24 August 2004

	Abstract

We magnetically imaged the magnetic action field (MAF) and optically imaged the transmembrane potentials generated by planar wave fronts on the surface of the left ventricular wall of Langendorff-perfused isolated rabbit hearts. The MAF images were used to produce a time series of two-dimensional action current maps. Overlaying epi-fluorescent images allowed us to identify a net current along the wave front and perpendicular to gradients in the transmembrane potential. This is in contrast to a traditional uniform double-layer model where the net current flows along the gradient in the transmembrane potential. Our findings are supported by numerical simulations that treat cardiac tissue as a bidomain with unequal anisotropies in the intra- and extracellular spaces. Our measurements reveal the anisotropic bidomain nature of cardiac tissue during plane wave propagation. These bidomain effects play an important role in the generation of the whole-heart magnetocardiogram and can not be ignored.

Key Words: SQUID microscopy, action current, biomagnetism, cardiac bidomain, electrophysiology, tissue anisotropy

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