Certain embodiments of the present invention disclose an implant with electrode line connections for the connection of intracardial and/or epicardial electrode lines, wherein the electrode line connections have together at least three electrical contacts of which at least one is associated with a right-ventricular electrode and another is associated with a left-ventricular electrode, an impedance determining unit (IMP) which has a current or voltage source (I) and a measuring device (U) for a corresponding voltage or current measurement operation, which is connected to the electrical contacts and possibly a housing electrode of the implant, in such a way as to afford a tri- or quadrupolar impedance measuring arrangement which includes exclusively ventricular electrodes and in addition possibly the housing electrode, wherein the impedance measuring arrangement produces impedance measurement values and is connected to an evaluation unit (EVAL) and the evaluation unit (EVAL) is adapted to ascertain a minimum of the impedance measurement values within a first time window (defined relative to a ventricular event) as end-diastolic impedance (EDZ) and a maximum of the impedance measurement values within a second time window as end-systolic impedance (ESZ).