Electrical impedance of layered atherosclerotic plaques on human aortas

Electrical impedance measurements were performed on 13 atherosclerotic human aortic segments at 67 measuring spots in order to determine whether or not on the basis of these data a distinction can be made between atherosclerotic lesions and normal tissue. The experimental results show that the apparent resistivity of an atherosclerotic spot does not necessarily deviate much from the resistivity of normal tissue. This is clarified by histology, which shows that the majority of lesions have a surface layer of connective, fibrous tissue having similar conducting properties to the normal arterial wall. A physical model of an atherosclerotic lesion is presented and compared with the data. Both experimental data and theoretical considerations lead to the conclusion that only when the superficial fibrous layer is absent or very thin in relation to the size of the measuring electrode is the measured resistivity at a lesion much higher than at normal spots.