An apparatus for controlling a flow of blood and/or other bodily matter in a patient's blood vessel comprises an implantable constriction device for gently constricting (i.e. without injuring the blood vessel) at least one portion of the wall of a blood vessel to influence the flow in the blood vessel, and a stimulation device for stimulating the at least one portion of the wall of the wall of the blood vessel. A control device controls the stimulation device to stimulate the wall portion, as the constriction device constricts the wall portion, to cause contraction of the at least one portion of the wall constricted by the constriction device to further influence the flow in the blood vessel. The apparatus can be used for restricting or stopping the blood flow in the blood vessel, or for actively moving the blood in the blood vessel, with a low risk of injuring the blood vessel.
