Aims: Our aim was to show that the propagation of the endogenous biopotential may be treated as the passage of electromagnetic wave through the physical medium and explained using a well-known theory for dispersive media. We also aimed at supporting theoretical predictions for such quantities as the wave velocity by direct measurement.
Methods: We derived the formula for the propagation of endogenous electromagnetic waves directly from Maxwell's laws and a formula for the refractive index widely used in optics. We hypothesized, that the wave propagates through the passive tissue involving all physical mechanisms for material polarization: ionic and non-ionic. In consequence, known data on bioimpedance spectra measurements may be used to estimate the properties of a unipolar ECG wave. Finally, we designed a simple experiment to confirm if the passage of unipolar potential obeys the derived rule.
Results: We were able to confirm by direct measurement that unipolar ECG potential propagation has a specific propagation velocity, similarly to any other electromagnetic wave propagating through a physical medium. For 150 measurements, the mean value of ECG potential propagation velocity equals 1500(700) m/s and it varies for different subjects. The result remains at an approximation level since we did not decompose the body into individual tissues and the low-frequency part of the bioimpedance spectrum, relevant to ECG frequencies, is poorly documented.
Conclusions: We conclude that our results allow to integrate the theory of bioimpedance with the theory of biopotential measurement. This brings an improved interpretation of various biopotential measurements. If a clear relation between passive conductance and the properties of the electromagnetic spectrum is further confirmed, it will unify the description of electrical phenomena within the body with the physical theories.