Intracardiac Impedance Plethysmography

Abstract

The impedance between electrodes implanted within the hearts of unanesthetized dogs fluctuates synchronously during the cardiac cycle, producing recorded patterns similar to those obtained by means of cardiometer. However, the impedance increased during systole as the distance between the electrodes decreased and was reduced during diastole. Since the recorded impedance was inversely related to the distance between electrodes, the thoracic tissues through which the current flowed cannot be considered as a homogenous conducting medium. The amplitude and configuration of the recorded patterns were often significantly altered by factors apparently unrelated to cardiac activity. Thus, this method is not suitable as a quantitative measure of linear or volumetric dimension of the ventricular chambers.