Heterogeneity of Micro- and Macro-conduction in Atrial Pectinate Muscles studied with Cardiac Near Field Measurements and Computer Simulation

Macro- as well as micro-conduction of the cardiac impulse propagation in Pectinate muscles from Rabbit hearts is studied by means of experiments and by means of computer simulation. Two simultaneous recordings of the cardiac near field E allow an estimation of global conduction times (macro) as well as the analysis of the microscopic local activation sequence at given sites. A monodomain 2D computer model based on a micrograph of the area of interest allows to simulate the virtual cardiac near field at any given site. Correlation of fine distortions and fractionations in extracellular signals then can be correlated to local particularities of microstructure not visible during an electrophysiological experiment. Experimentally we found that the visible macrostructure of the network often is discordant with the signal characteristic, a discrepancy only plausible by effects of microstructure. The computer simulation results based on micrographs confirm this hypothesis.