Quantitative characterization of the relief of body surface potential distribution.

The body surface distribution of the cardiac electric field is best represented as reliefs of positive and negative potentials, or their time integrals. The objective of this study was to design a methodology of their quantitative evaluation. QRST isointegral maps were obtained from 45 healthy subjects (35 men, 10 women, aged 10-67 years) using a 80 electrode set. Relative frequencies of positivity and of negativity were ascertained for different levels of the QRST integral values. Two fuzzy subsets: that of positive and that of negative QRST values were defined on the set of electrode placements. The values of membership functions of their elements were derived from relative frequencies obtained in the reference group of subjects, separately for all levels of QRST integral values. Statistics of these values characterize the reference reliefs of the positive and of the negative QRST values and are used to test their resemblance to a given individual distribution. In conclusion, the representation of isopotential, or isointegral body surface potential maps as reliefs of their positive and negative values, based on the theory of fuzzy sets, enables a quantitative evaluation of their resemblance to a given individual distribution. (Fig. 6, Ref. 18.)