An implantable electrostimulation device having at least three input channels, (each forming a sensing channel), which are each connected to at least one electrode or to one terminal for an electrode, using which at least three different electrical potentials accompanying an excitation of cardiac tissue (myocardium) in a heart may be detected. Uses a signal processing unit which is connected to the input channels and is implemented to analyze the time curve of the potentials detected via the three sensing channels as three input signals in chronological relation to a periodically repeating trigger signal, which triggers a time window, and which is also implemented to detect predefined signal features for each of the three input signals within the time window triggered by the trigger signal, store them, and compare them to corresponding signal features of preceding time windows or of another input channel within the same time window.