An electrostimulator having electrode connections which are to be connected, at least at times, to a stimulation unit and to a detection unit of the electrostimulator. The stimulation unit is adapted to generate electrostimulation pulses for the stimulation of body tissue and to deliver the electrostimulation pulses to at least one of the electrode connections. The detection unit is adapted to detect successful stimulation of body tissue on the basis of an electrical signal occurring at least one of the electrode connections. The electrostimulator is adapted to record an electrical signal representative of an intracardial electrocardiogram by way of the at least one electrode connection. Arranged between the electrode line connection and the detection unit is a high pass filter with a lower limit frequency of greater than 100 Hz, and the detection unit is adapted to evaluate the high pass-filtered electrical signal.