Don Marlowe discusses procedures for durability testing of prosthetic heart valves with Committee F04 Vice Chairman Dan Chwirut in OST's engineering laboratories. Since the long-term durability of medical implants can never be determined a priori by clinical trials, most implants are subjected to accelerated bench testing prior to FDA approval. Mechanical heart valves, while expected to last indefinitely in vivo, are tested at severely elevated pressures for 600 million cycles (15 years equivalent). Manufacturers generate the data, for FDA review and approval, in accordance with test methods developed as consensus standards.