Three-dimensional mapping of electrical propagation in the heart: experimental and mathematical model based analysis

Extended laser scanning confocal microscopy has recently been used to reconstruct the discontinuous laminar organisation of cardiomyocytes in a block of rat left ventricle. The confocal data allowed delineation of intercellular clefts or cleavage planes which coursed through the tissue block. This study describes a finite element model of electrical propagation which permitted the accurate incorporation of the structural discontinuity apparent in the tissue reconstruction. The effects of the cleavage planes on propagation from focal activation in the midwall, and on the response to a defibrillation-strength shock were examined. It is concluded that the laminar organisation of myocytes may lead to orthogonal anisotropy of electrical properties about microstructurally defined axes. In addition, structural discontinuity gave rise to complex polyphasic extracellular potentials, and asymmetric propagation from a focal activation. During application of shock, the cleavage planes acted as a substrate for far field stimulation, which was responsible for activation of the bulk myocardium within the duration of the applied current.