Abstract
Innovative cardiac performance evaluation methods require simultaneous absolute pressure and volume. Impedance catheter volumetry determines volume by measuring intracavitary potentials generated along the catheter by an impressed current in the left ventricular blood volume, but the conventional method can exhibit unacceptable absolute errors (>50%). Deterministic estimators were developed from field theory to determine geometry and myocardial conductivity from potential measurements alone. These worked in noise-free, spherical and spheroidal models but failed with measurement noise. Utilizing statistical training data allowed incorporating a priori information concerning the relationship between potentials and volume in a given ventricle. This procedure resulted in volume estimates that were not highly sensitive to noise. Both in model simulations and animal testing, error reductions of over 50% were observed, yielding absolute volumes accurate to 15–20%.
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