Effects of cardiac microstructure on propagating electrical waveforms.

Electrical waveforms measured during propagation at microscopic level are considerably affected by normal variations in cardiac microstructure as well as by the superfusing fluid. On the basis of evidence we present in this article, we argue that the anisotropic waveform variations discussed here are explained primarily by the associated variations in different microstructural components of myocardial architecture rather than by the effects of the perfusing bath. The results suggest that different components of myocardial architecture have preferential effects on f1.gif" BORDER="0">(max) and on the shape of the foot of the transmembrane action potential (V(m) foot). Resistive discontinuities primarily affect f1.gif" BORDER="0">(max), and an additional capacitive component in the local circuit due to the capillaries in interstitial space primarily affects V(m) foot. Resistive discontinuities also have an important influence on cardiac conduction. These discontinuities include spatial variations in the size of interstitial space (interstitial resistive discontinuities) and the role of cellular scaling (effects of cell size) when changes occur in the cellular and multicellular distribution of gap junctions during remodeling of normal mature myocardium to proarrhythmic structural substrates. The full text of this article is available at http://www.circresaha.org.