An implantable cardiac stimulator includes at least one first sensing unit for detecting intrinsic cardiac activities of a first ventricle, at least one ventricular stimulation unit for stimulating a second ventricle, and a stimulation control unit connected to the first sensing unit. The stimulation unit processed output signals of the first sensing unit and generates control signals for the stimulation units. The stimulation control unit derives a current intrinsic RR interval from detected ventricular intrinsic cardiac activities R of the first ventricle, and to determine from the RR interval a delay interval Δ, which begins with a ventricular event of the first ventricle and at the end of which the stimulation control unit triggers a stimulation of the second ventricle (unless it is suppressed).
