Fatigue Evaluation of a Prosthetic Heart Valve

Approximately 86,000 Björk-Shiley convexo-concave (BSCC) heart valves were implanted from 1979 to 1984 and approximately 1% of these valves experienced failure due to fatigue of a critical valve component. Failures of this type are likely to yield a 70% mortality rate in patients. Although the BSCC valve was constructed from a material that possesses good fatigue properties continued operation of the valves produced cracking under certain circumstances suggesting that a small subset of valves may operate under conditions that are close to the boundary between continued safe operation and catastrophic failure. To understand the conditions that produced failure, a detailed engineering assessment has been conducted to identify the influence of valve design, manufacturing processes and physiologically related loading conditions on the potential for valve failure. Intimately coupled computational analysis procedures of the fluidstructure interaction were used to define loading of the outlet strut during valve closure. Standard structural and fracture mechanics analyses of the valve were used to identify the influence of design changes on the magnitude of the stresses at critical locations in the valve.