An anonymous reader writes "Serious heart surgery usually involves stopping the organ and keeping the patient alive with a cardiopulmonary bypass machine. But this risks brain damage and requires a long recuperation. Scientists at Harvard University and Children's Hospital Boston have now developed a device that lets surgeons operate on a beating heart with a steady hand. The 'robotic' device uses 3-D ultrasound images to predict and compensate for the motion of the heart so that the surgeon can work on a faulty valve as it moves. The approach should improve recovery times and give a surgeon instant feedback on the success of the procedure, the researchers say. Here's a (slightly gory) video of the device in action."