The present invention relates to an implantable heart help device for assisting the pump function of the heart by exerting an external force on the heart. The device is provided with a first fixating member adapted to be fixate the device to a part of the human body comprising bone, a heart pump device having a surface adapted to contact and exert an external force on the heart, a second fixating member in contact with the heart pump device. The second fixating member is displaceable in relation to the first fixating member for changing the position of the surface of the heart pump device, to allow the surface of the heart pump device to contact and exert the external force on at least two different positions on the heart.