Abstract: Heart events are identified within an electrical signal derived from the heart by determining when the signals exceed a threshold which is matched to the signal height of the electrical signal dependent on a chronological average value of the detection margins of the signal that exceed the threshold in successive detection events. In order to suppress the influence of noise-like disturbing signals that appear in isolation on the control of the threshold but to nonetheless achieve an adequately fast adaptation of the threshold to rapid, substantial changes of the electrical signal despite the formation of an average value, the formation of the average value ensues over a time interval corresponding to the duration of only a few breaths and a change of the threshold ensues only when the average value respectively upwardly or downwardly transgresses upper or lower the limit values of a switching hysteresis.