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Use of a differentiable model for localization of ventricular surface activation map critical points: Numerical simulations and animal experiments

A new approach to rendering the ventricular surface activation isochrones has been proposed wherein the array of body surface potentials (BSP) is used to localize critical points of ventricular surface activation individually, thereby constraining and regularizing the full inverse problem while avoiding the need to specifically treat ill-conditioned transfer matrices. The method relies on time differentiation of BSP, a very noise-amplifying process. Using numerical simulations, regularization of differentiation, and taking advantage of the method's inherent opportunities for employing model-based parameter estimation methods, we have found that the general signal-to-noise requirements of the approach are within the known capabilities of electrocardiogra-phy. While a principal theoretical difficulty of the approach relates to the ability to recognize "step discontinuities" in spatially averaged time derivatives of BSP, experiments in five pigs found consistent associations between steep deflections in the averaged derivatives and critical points of concurrently recorded epicardial activation maps, also supporting the practical feasibility of the method.