This invention is directed to a partitioning device for separating a chamber of a patient's heart into a productive portion and a non-productive portion. The device is particularly suitable for treating patients with congestive heart failure. The partitioning device has a frame-reinforced, expandable membrane which separates the productive and non-productive portions of the heart chamber. Elements of the frame include ribs that are secured to the expandable membrane, to form an integrated structure that may be unilaminar or bilaminar in form. The proximal ends of the ribs of the frame have tissue-penetrating elements about the periphery thereof which are configured to penetrate tissue lining the heart wall at an angle approximately perpendicular to a longitudinal axis of the partitioning device. The partitioning device has a hub with a non-traumatic distal end to engage the ventricular wall.