An artificial valve (5; 10; 20; 30; 50) for implantation in a mammal body, in or adjacent to a mammal blood vessel, the artificial valve comprising a casing (12; 37; 61) and an opening and closing mechanism, with at least part of said opening and closing mechanism being at least a first moving part (11; 21, 22; 31, 32, 33; 51) adapted to make an opening and a closing movement relative to the casing (12; 37; 61), said movements comprising movements to assume an open and a closed position for opening and closing, respectively, of the blood flow through said blood vessel, as well as positions between said open and closed positions, said closing movement of the first moving part (11; 21, 22; 31, 32, 33; 51) being initiated and carried out as the result of a predefined threshold value being reached by a physical parameter of the mammal or a functional parameter of a device used by the mammal, the physical or functional parameter being one or more of the following: • the blood pressure on an inner or an outer side of the valve or the difference in blood pressure between an inner and an outer side of the artificial valve in its closed position, • the blood flow at a defined point in the circulatory system of the mammal, • a physical parameter which is related to the contraction of a muscle at a defined point in the mammal, • a body generated parameter related to the contraction of the mammal's heart muscle, • a device generated signal related to the contraction of the mammal's heart muscle, wherein the opening and closing mechanism is adapted to be powered in its movements to the open and/or closed position in part or entirely by a power source which is external to the blood vessel, wherein the opening, closing or opening and closing becomes an active measure, characterized in that the power source comprising a plurality of coils and adapted to interact with at least one magnet placed on the moving part, wherein the plurality of coils are adapted to be energized stepwise with two or more energy pulses to affect the at least one magnet on the moving part, for operating the valve to perform the valve movements to assume said open or closed position, or the power source comprising a single coil and adapted to interact with a plurality of magnets placed on the moving part, wherein the single coil is adapted to be energized stepwise with two or more energy pulses to affect the plurality of magnets on the moving part, for operating the valve to perform the valve movements to assume said open or closed position. • the blood pressure on an inner or an outer side of the valve or the difference in blood pressure between an inner and an outer side of the artificial valve in its closed position, • the blood flow at a defined point in the circulatory system of the mammal, • a physical parameter which is related to the contraction of a muscle at a defined point in the mammal, • a body generated parameter related to the contraction of the mammal's heart muscle, • a device generated signal related to the contraction of the mammal's heart muscle, wherein the opening and closing mechanism is adapted to be powered in its movements to the open and/or closed position in part or entirely by a power source which is external to the blood vessel, wherein the opening, closing or opening and closing becomes an active measure, characterized in that the power source comprising a plurality of coils and adapted to interact with at least one magnet placed on the moving part, wherein the plurality of coils are adapted to be energized stepwise with two or more energy pulses to affect the at least one magnet on the moving part, for operating the valve to perform the valve movements to assume said open or closed position, or the power source comprising a single coil and adapted to interact with a plurality of magnets placed on the moving part, wherein the single coil is adapted to be energized stepwise with two or more energy pulses to affect the plurality of magnets on the moving part, for operating the valve to perform the valve movements to assume said open or closed position.