A device for treating an aneurysm of a human or mammal patient, wherein the aneurysm may self-expand, leading to the aneurysm bursting with high risk for death of the human or mammal patient. The device comprising an implantable member adapted to be placed in connection with the outside of a blood vessel having the aneurysm, and to exercise a pressure on the outside of the blood vessel having the aneurysm, a measuring device or sensor for measuring or sensing an expansion of the aneurysm, and a pressure regulator adapted to regulate the exercised pressure on the outside of the blood vessel having the aneurysm.