An apparatus for controlling a flow of blood in a blood vessel formed by a tissuewall of a patient's blood vessel comprises an implantable constrictiondevice for gently constricting (i.e. without substantially hampering the bloodcirculation in the tissue wall) at least one portion of the tissue wall to influencethe flow in the blood vessel, and a stimulation device for stimulating the wallportion of the tissue wall. A control device controls the stimulation deviceto stimulate the wall portion, as the constriction device constricts the wallportion, to cause contraction of the wall portion constricted by the constrictiondevice to further influence the flow in the blood vessel. The apparatus can beused for stabilizing, treating or controlling an aneurysm, with a low risk ofside- effects, such as injuring the blood vessel or causing embolism.
