Significance
Heart valves play a critical role in regulating blood flow through the cardiovascular system. Diseases of the heart valve can either be congenital or caused by infections such as rheumatic fever or endocarditis. Problems could also arise simply as a consequence of aging. One of the more common popular mechanical devices that was implanted extensively between 1979 and 1986 is the Bjork-Shiley Convexo-Concave (BSCC) valve. The BSCC valve consists of a pyrolytic carbon disc that serves as an occluder to block the flow of blood in one direction but allows flow in the other direction. The valve employs two struts to hold the disc in place. The outlet strut is TIG welded to the suture ring while the inlet strut is integral to the ring. The failure of the other weld can cause the strut to separate from the suture ring, thereby allowing the disc to detach from the valve.
Objective
Development of inspection methods for TIG-welded struts in artificial heart valves.
Approach
Two simple electromagnetic methods may be used for detecting strut fractures in prosthetic heart valves. The first method involves immersing the heart valve in a uniform time varying electromagnetic field and measuring the perturbation of the field in regions proximate to the strut. The second method that is currently being investigated involves the use of electromagnetic-acoustic transduction methods for exciting the resonant modes of the outlet strut. Differences between the frequencies associated with the resonant modes of intact and fractured struts are exploited to diagnose the state of the valve.