Electrotherapy device

An implantable electrotherapy device comprising:

• a housing which has an electrode line connection for the connection of at least one electrode line which is to be placed intracardially and which has at least one measuring electrode for recording an intracardiac impedance signal;
• an activity sensor, arranged in the housing, which is adapted to produce an activity level signal whose respective activity level signal values in the implanted condition of the therapy device depend on a physical activity of a patient;
• an impedance or conductivity measuring unit, arranged in the housing, which is adapted to produce a unipolar or bipolar impedance or conductivity signal by measuring an impedance or conductivity value between a neutral electrode and a measuring electrode or between two measuring electrodes;
• and
• an evaluation unit, arranged in the housing, wherein the evaluation unit is connected to the impedance or conductivity measuring unit and the activity sensor and is adapted for evaluating the impedance or conductivity pattern signal produced by the impedance or conductivity measuring unit and the respectively time-associated activity level signal and for producing and delivering a contractility signal, in such a way that the contractility signal is derived from the impedance or conductivity signal and the activity level signal and reflects the respective contractile state of a heart associated with an activity level signal value.