A diagnostic device for determining the amount of change required in a coronary sinus to reduce valve regurgitation. The device includes a distal tube having a distal anchor at a distal end portion of the distal tube, a proximal tube having a proximal anchor at a distal end portion of the proximal tube, and an adjustor to move the distal tube relative to the proximal tube. The proximal tube and the distal tube together form a telescoping elongate body adapted to fit within the coronary sinus, and the device includes a scale to measure the movement of the distal anchor relative to the proximal anchor.