An operating method for an implantable cardiologic device comprises the following steps for detection of a significant event or condition a patient is subject to: measurement of intracardiac impedance; detection of the morphologic signal course of the impedance, based on at least two morphologically representative parameters of the signal course; continuous storage of the parameter data from a defined measuring period; computation of a correlation coefficient for the stored parameter data; and comparison of the correlation coefficient with a reference correlation coefficient, with transgression of a defined deviation of the correlation coefficient from the reference correlation coefficient indicating the presence of a significant event.