Health Sciences · Temerty Faculty of Medicine
A small (4.4 cm square) clear plastic case with a hinged lid contains a circular artifact, a tilting disk heart valve. The rim of the valve is covered in a white fabric (Teflon). Mounted in this metal frame is a circular black plate with a circular recess at its centre. This is retained on either side by a metal strut that attaches to the surrounding frame.
The interior of the case is partly filled with green particles resulting from a decomposing foam pad.
A small piece of translucent tape adheres to the top surface of the case.
Accession Number: 2020.med.11
Alternative Name: Mechanical Heart Valve (MHV)
Primary Materials: Plastic, Metal
Markings:
Dimensions (cm): Height = 3, Width = 4.4, Length = 4.4.
The Björk–Shiley heart valve was an early example of a low-profile tilting-disc prostheses. Such valves employ a captive disk that is retained on either side by an inlet strut and an outlet strut.
The disk was marketed as the Björk-Shiley convexo-concave (BScc) valve due to the convexo-concave shape of the valve disk. This was designed to permit a smoother flow of blood in order to reduce the likelihood of thrombus formation relative to an earlier design (Blackstone 2005, 2717).
The valve was introduced in 1979 and withdrawn in 1986 after a significant number of outlet strut fractures (OSFs). The valve gained considerable attention in the media and became an object lesson of failure in biomedical engineering.
Good: The surface of the clear case is slightly dirty and very lightly scuffed. Particles from a decomposing foam pad are loose inside the case and adhere to the heart valve within.
Associated Instruments:
Manufacturer: Shiley Inc., Irvine, California.
Date of Manufacture: c. 1979 – 1986s.
This artifact belongs to a small collection of items related to cardiac surgery that was collected by Dr. Wilfred Gordon “Bill” Bigelow (1913 – 2005). After his death, the collection was donated to the Cardiovascular Sciences Collaborative Program of the University of Toronto, where it is currently on display.
Eugene H. Blackstone (2005). “Could It Happen Again? The Björk-Shiley Convexo-Concave Heart Valve Story.” Circulation, 111, 21: 2717.
Donald C. Harrison, Michel A Ibrahim, Arthur E Weyman, Lewis H Kuller, William J Blot, and David E Miller (2013).“The Björk-Shiley Convexo-Concave Heart Valve Experience from the Perspective of the Supervisory Panel.” The American Journal of Cardiology, 112, 12: 1921–31.
Denton A. Cooley (2010). “In Memoriam: Donald P. Shiley: 1920–2010.” The Texas Heart Institute Journal 37(6): 627–8.
Tony Perry (7 August 2010) “OBITUARIES; DONALD P. SHILEY, 1920 – 2010; Co-Inventor of Innovative Heart Valve.” Los Angeles Times.
Viking O. Björk (1990) “Development of an artificial heart valve.” The Annals of Thoracic Surgery 50(1): 151-154.
John H. Fielder (1993). “Getting the Bad News about Your Artificial Heart Valve.” The Hastings Center Report 23(2): 22–28.
Donald P. Shiley (1920 – 2010) was born in Yakima, Washington and studied Engineering and Chemistry at the University of Portland, graduating in 1951. In the late 1950s, he was employed by Edwards Laboratories of Santa Ana, California (founded 1958) where the early Starr-Edwards (SE) mitral valve was developed (see Perry 2010).
Shiley founded Shiley Laboratories in Irvine, California in 1964 with the development of an artificial heart valve. He entered into collaboration with Viking O. Björk (1918 – 2009), a Swedish cardiac surgeon with extensive experience in transplanting heart valves. The origins of the Björk–Shiley design are, no doubt, complex. Cardiac surgeon Denton A. Cooley mentions being shown a prototype caged tilting disk valve prior to Shiley’s collaboration with Björk (See Cooey 2010, 627). Björk’s detailed account of the design’s evolution mentions his own early experience using a Kay-Shiley flat disc valve, designed as a collaboration between Shiley and cardiac surgeon Dr. Jerome Kaye (1921 – 2015). This preceded his own collaboration with Shiley (Björk 1990, 151).
The design developed by Björk and Shiley evolved incrementally. In 1974, Shiley inc. introduced a radial spherical (R/S) valve, which, like the later Björk–Shiley (BScc) model, was a disk valve retained by two struts. This proved susceptible to valve thrombosis, the production of blood clots due to turbulent blood flow through the valve. The BScc was introduced in 1978 in response to this issue. A monostrut version was later developed, with a larger 70° valve opening angle, though this was not approved for use in the United States. In 1979, Shiley Inc. was purchased by Pfizer inc., which took over manufacturing of the implant. Approximately 86,000 BScc valves were implanted worldwide (Blackstone 2005, 2717).
Outlet strut fractures (OSFs) occurred during the device’s premarket trial and continued throughout its period in use. The device was withdrawn in 1986 amidst legal proceedings involving hundreds of device failures. The source of the failure was eventually traced to unexpectedly high bending stresses on the outlet strut due to closing disk impacts (Blackstone 2005, 2717).
The situation was complicated by the fact that replacing the valve incurred a substantially higher risk than leaving it in place. The result was that thousands of patients were left to live with devices with a small chance of catastrophic failure. The stress that this incurred was reflected in financial penalties to Pfizer on behalf of patients with functioning implants. Failures in the approval of, and response to, the BScc valve, led to the American Safe Medical Device Act of 1990 (Fielder 1993, 24-26).