FACC is Fellow of the American College of Cardiology. It means that your cardiologist completed a certain number of hours, performed a certain number of specific procedures, and that sorta thing, and was awarded fellowship.
Similarly other specialties have their fellows: FACS (American College of Surgeons), FAAP (American Academy of Pediatrics), FACOG (American College of Obstetrics and Gynecology), FACEP (American College of Emergency Physicians), FACP (American College of Physicians), etc.
Tim W. of N.Y.C.