A medical device that can be used for treating a defective heart valve. One aspect of the invention pertains to a longitudinally adjustable medical device that comprises a distal portion, a proximal portion, and a cord member. The distal portion comprises a distal anchoring member, a distal telescope, and a distal backbone. The proximal portion comprises a proximal anchoring member, a proximal telescope, and a proximal backbone. The distal backbone and the proximal backbone are configured to provide a structural support to the device while providing flexibility to the device. The cord member is disposed within the device and used to facilitate longitudinal adjustment for the device.