Model study of vector-loop morphology during electrical mapping of microscopic conduction in cardiac tissue

The large variety in loop morphology of potential differences recorded at t he cardiac surface has been generally attributed to structural discontinuit ies of the tissue. The aim of this work was to examine if the diversity of vector loops of the electric field E found experimentally may also arise du ring continuous anisotrope conduction. For this purpose a monodomain comput er model was used, consisting of a two-dimensional sheet of excitable tissu e surrounded with an unbounded volume conductor. Close to the tissue surfac e our computations predicted a narrow biphasic course of Phi (e) with peak- to-peak separation of less than 400 mum. We examined how accurately E could be reconstructed from measurements recorded with four-element electrode ar rays and how activation sequence, interelectrode spacing, and probe orienta tion affects the results. We found "closed" vector loops of E in planar, an d at the apex of elliptical wave fronts, whereas outside of these regions v ector loops were "open." Varying probe orientation and size resulted in sub stantial changes of vector-loop morphology. We concluded that close to the cardiac current sources accurate measurement of E would require interelectr ode distances of less than 100 mum. (C) 2000 Biomedical Engineering Society . [S0090-6964(00)01010-9].