A BIDOMAIN MODEL WITH PERIODIC INTRACELLULAR JUNCTIONS - A ONE-DIMENSIONAL ANALYSIS

The classical bidomain model of cardiac tissue views the intracellular and extracellular (interstitial) spaces as two coupled but separate c ontinua. In the present study, the classical bidomain model has been e xtended by introducing a periodic conductivity in the intracellular sp ace to represent the junctional discontinuity between abutting myocyte s. In this model the junctional region of a myocyte is represented in a way that permits variation of junction size and conductivity profile . Employing spectral techniques, a new method was developed for solvin g the coupled differential equations governing the intracellular and e xtracellular potentials in a tissue preparation of finite dimensions. Different spectral representations are used for the aperiodic intra- a nd extracellular potentials (finite Fourier integral transform) and fo r the periodic intracellular conductivity (Fourier series). As a first application of the method, the response of a 50-cell, single interior fiber to a defibrillating current is examined under steady-state cond itions. Transmembrane as well as intra- and extracellular potential di stributions along the fiber were calculated.