Three-dimensional activation mapping in ventricular muscle: Interpolation and approximation of activation times

Interpolation plays an important role in analyzing or visualizing any scala r field because it provides a means to estimate field values between measur ed sites. A specific example is the measurement of the electrical activity of the heart, either on its surface or within the muscle, a technique known as cardiac mapping, which is widely used in research. While three-dimensio nal measurement of cardiac fields by means of multielectrode needles is rel atively common, the interpolation methods used to analyze these measurement s have rarely been studied systematically. The present study addressed this need by applying three trivariate techniques to cardiac mapping and evalua ting their accuracy in estimating activation times at unmeasured locations. The techniques were tetrahedron-based linear interpolation, Hardy's interp olation, and least-square quadratic approximation. The test conditions incl uded activation times from both high-resolution simulations and measurement s from canine experiments. All three techniques performed satisfactorily at measurement spacing less than or equal to 2 mm. At the larger inter-electr ode spacings typical in cardiac mapping (1 cm), Hardy's interpolation prove d superior both in terms of statistical measures and qualitative reconstruc tion of field details. This paper provides extensive comparisons among the methods and descriptions of expected errors for each method at a variety of sampling intervals and conditions. (C) 1999 Biomedical Engineering Society . [S0090-6964(99)01105-4].