Pacemaker with periodic modulation of single stimulation intervals

Heart pacemaker having a device for measuring at least one cardiac function parameter and a device in such a periodically modulated single stimulation intervals, that the degree of modulation will be dependent on both the duration of the diastolic interval and from the evoked by the modulation changes in the cardiac function parameter so that certain phases of the electrical and mechanical restitution can be scanned independently of the systole and with consistent accuracy.