This paper considers the applicability of effective conductivity measurements for monitoring physiological and/or pathological phenomena induced by ischemia in the myocardium. The sensitivity of a probe, calculated by means of the finite element method, to changes in the conductivity of the tissue examined is defined for this purpose. Probes developed by Schafer and collaborators (1995) and in our own departments have been examined on the basis of this sensitivity. Theoretical results were verified experimentally using a tank, enlarged models of the probes, and a specially developed electronic circuit. It follows from this study that the probe developed by Schafer et al. is characterized by positive and negative sensitivity. This can lead to misinterpretation of the measurements obtained. In contrast, the sensitivity of our probe is dominantly positive. An example of the in vivo result obtained during experimentally induced ischemia in a swine heart is included.