At least one embodiment of the invention relates to a cardiac stimulator comprising at least one stimulation unit to deliver subthreshold stimulation pulses for a cardiac contractility modulation therapy via at least two stimulation electrode poles, and at least one sensing unit to detect cardiac electrical or mechanical actions. The at least one sensing unit detects signals characteristic of cardiac action and comprises, or is connected to, an evaluation unit that evaluates signals detected by the sensing unit and supplies a corresponding evaluation result signal. The cardiac stimulator further comprises a therapy control unit to control a respective cardiac contractility modulation therapy depending on a respective evaluation result signal. A respective cardiac contractility modulation therapy is activated/deactivated depending on a stimulation success/failure of a suprathreshold stimulation, and/or therapy parameters of a respective cardiac contractility modulation therapy are selected and/or adjusted depending on the respective evaluation result signal.
