Nancy Clayton is one of the first people in the world to receive a new catheter-based device designed expressly to replace a diseased mitral valve. It’s a two-stage design, with an anchoring ring installed separately from the valve itself. Each part can be withdrawn and repositioned repeatedly for a better fit. “With other devices, once you’ve placed it, you’re done,” explains Clayton’s surgeon, Mathew Williams, MD, a pioneer in heart valve repairs. “There’s no retrievability.” Mitral valve regurgitation, in which the valve’s leaflets fail to close properly, is the most common form of valve disease, affecting an estimated 4 million Americans. Of the 1.7 million candidates who are eligible for mitral-valve surgery each year, only 30,000 undergo it, largely because they are too frail to endure invasive surgery.