VALIDATION OF 3-DIMENSIONAL CONDUCTION MODELS USING EXPERIMENTAL MAPPING - ARE WE GETTING CLOSER

The anisotropic material properties, irregular geometry, and specializ ed conduction system of the heart all affect the three-dimensional (3D ) spread of electrical activation. A limited number of research groups have tried accounting for these features in 3D conduction models to i nvestigate more thoroughly their observations of cardiac electrical ac tivity in 3D experimental preparations. The full potential of these la rge scale conduction models, however, has not been realized because of a lack of quantitative validation with experiment. Such validation is critical in order to use the models to predict the electrical respons e of the myocardium to drugs or electrical stimulation. In this paper, a quantitative, experimental validation of paced activation in a 3D c onduction model of a 3 cm x 3 cm x 1 cm section of the ventricular wal l is presented. Epicardial and intramural pacing stimuli were applied in the center of a 528 channel electrode plaque sutured to the left ve ntricle in dogs. Unipolar electrograms were recorded at 2 kHz during a nd after pacing. Fiber directions within the tissue below the electrod es were estimated histologically and from pace-mapping. Simulated epic ardial electrograms were computed for surface paced beats using our 3D bidomain model of the mapped tissue volume incorporating the measured fiber directions. Extracellular potentials and isochronal maps result ing from paced activations in both model and experiment were directly compared. Preliminary results demonstrate that our 3D model reproduces qualitatively such key features of the experimental data as electrogr am morphologies and epicardial conduction velocities. Though quantitat ive agreement between model and experiment was only moderate, the vali dation approach described herein is an essential first step in assessi ng the predictive capability of present day conduction models. (C) 199 8 Elsevier Science Ltd. All rights reserved.