An annuloplasty device for treating a defective mitral valve having an annulus, comprising a removable and flexible elongate displacement unit for temporary insertion into a coronary sinus adjacent the valve, wherein the displacement unit has a delivery state for delivery into the CS, and an activated state to which the displacement unit is temporarily and reversibly transferable from said delivery state, a proximal reversibly expandable portion being reversibly foldable to an expanded state for positioning against a tissue wall at the entrance of the CS, wherein the displacement unit comprises a distal anchoring portion being movable in relation to the proximal expandable portion in a longitudinal direction of the displacement unit to said activated state in which the shape of the annulus is modified to a modified shape when inserted in the CS, a stent arranged around the displacement unit and being movable relative the displacement unit along the longitudinal direction for insertion into the CS, and wherein the stent is releasably connected to a delivery device and arranged radially between the displacement unit and the proximal expandable portion in a radial direction, the radial direction being perpendicular to the longitudinal direction, characterized in that the proximal expandable portion is connected to a sheath and is configured to be expanded in the radial direction by pushing a proximal portion of the sheath towards the distal anchoring portion, the annuloplasty device comprising a catheter to enclose the stent and position the stent relative the displacement unit in the longitudinal direction, wherein the stent is ejectable from, and retrievable into, the catheter by the delivery device, wherein the catheter is movable over the displacement unit and inside said sheath in the longitudinal direction, in said activated state. a removable and flexible elongate displacement unit for temporary insertion into a coronary sinus adjacent the valve, wherein the displacement unit has a delivery state for delivery into the CS, and an activated state to which the displacement unit is temporarily and reversibly transferable from said delivery state, a proximal reversibly expandable portion being reversibly foldable to an expanded state for positioning against a tissue wall at the entrance of the CS, wherein the displacement unit comprises a distal anchoring portion being movable in relation to the proximal expandable portion in a longitudinal direction of the displacement unit to said activated state in which the shape of the annulus is modified to a modified shape when inserted in the CS, a stent arranged around the displacement unit and being movable relative the displacement unit along the longitudinal direction for insertion into the CS, and wherein the stent is releasably connected to a delivery device and arranged radially between the displacement unit and the proximal expandable portion in a radial direction, the radial direction being perpendicular to the longitudinal direction, characterized in that the proximal expandable portion is connected to a sheath and is configured to be expanded in the radial direction by pushing a proximal portion of the sheath towards the distal anchoring portion, the annuloplasty device comprising a catheter to enclose the stent and position the stent relative the displacement unit in the longitudinal direction, wherein the stent is ejectable from, and retrievable into, the catheter by the delivery device, wherein the catheter is movable over the displacement unit and inside said sheath in the longitudinal direction, in said activated state.