When a dentist named Barney Clark received a permanent artificial heart in 1982, it was hailed as a medical miracle. To the public and the press, he represented hope and a huge leap forward in fighting the world’s biggest killer: heart disease. But hope turned to controversy as Clark and other patients suffered a series debilitating complications and critics called the medical experiment cruel and unethical. Eventually the FDA said no more permanent heart implants and the device faded from public view. But it was hardly the end of the story, for the artificial heart continues to impact medical science in surprising ways.