A method of treating a mitral valve without open-heart surgery is disclosed. An expandable prosthesis comprises an anchoring portion and an occluding member coupled to the anchoring portion. The prosthesis is loaded into a distal end of a delivery catheter and advanced through a femoral vein and through a pre-made puncture in an atrial septum. The occluding member is then positioned in the mitral valve and the anchoring portion is positioned in the left atrium for maintaining the occluding member between the leaflets of the mitral valve. After deployment, the occluding member prevents blood from flowing from the left ventricle to the left atrium during systole.