Defects and deceptions-the Bjork-Shiley heart valve

The development of mechanical heart valves is one of the success stories of contemporary medicine. Many people with diseased heart valves become seriously disabled and soon die unless a prosthetic valve can be installed. Shiley, Inc., later a subsidiary of Pfizer, was a pioneer in the development of mechanical heart valves. In 1974 the company developed a radial spherical (R/S) valve, consisting of a disk held in place by two wire struts, allowing it to swing open and closed in response to blood flow. The struts are welded to a metal ring, which is covered with a cloth sewing ring for attachment to the heart. In 1979 Shiley introduced a similar valve, the 60/spl deg/ Convexo-Concave (C/C), which it believed would improve blood flow through the valve. In this valve, the inlet strut was an integral part of the metal ring and only the outlet strut was welded. A C/C valve that opened to 70/spl deg/ was also manufactured, but it was not approved for sale in the US. The original C/C valve was withdrawn from sale due to a less than 1% failure rate. The ethical, legal and moral issues of this decision are discussed.