Implantable medical devices evaluating thorax impedance

An implantable medical device comprising:

• an impedance determination unit comprising
• a constant current source or a constant voltage source having current feed terminals that are connected or can be connected to electrodes for intracorporal placement and that is adapted to generate measuring current pulses having a constant current strength or a constant voltage, respectively, for causing a current to be fed through a body via intracorporally placed electrodes;
• a measuring unit for measuring a voltage corresponding to a current fed through a body by said constant current source or a current strength of a current fed through a body by said constant voltage source, respectively;
• an impedance value determination unit that is connected to said constant current source or said constant voltage source and the measuring unit that is adapted to determine an impedance value for each measuring current pulse;
• and,
• an impedance measuring control and evaluation unit, that is connected to said impedance determination unit and that is adapted to control said impedance determination unit and to evaluate a sequence of consecutive impedance values determined by said impedance determination unit, wherein the impedance determination unit is further adapted to determine at least intrathoracic impedance values and intracardiac impedance values for same period of time, wherein the intrathoracic impedance values are sampled with a lower sampling rate than the intracardiac impedance values.