Pfizer purchased Shiley in 1979 at the onset of its Convexo-Concave valve ordeal, involving the Bjork–Shiley heart valve. Approximately 500 people died when defective valves failed and, in 1994, the United States ruled against Pfizer for ~$200 million.
Attempts to improve the design of the valve and speed manufacturing, however, led to a weaker structure, with serious consequences. Beginning in 1979, Bjork–Shiley valves with the convexo-concave design had a tendency to develop fractures in the outflow strut which could result in catastrophic valve failure and possibly sudden cardiac death. Later analysis revealed that the strut was fracturing at the place where it was welded onto the metal valve ring. One end of the strut would fracture first, followed by the second strut some months later. Eventually, 619 of the 80,000 convexo-concave valves implanted fractured in this way, with the patient dying in two thirds of those cases. The convexo-concave valve was forced off the market by the FDA in 1986.[2] Valves welded by specific welders were at greater risk of fracture. The Convexo-Concave valve was withdrawn from the market and multiple lawsuits filed. This recall and legal struggle have been described as "perhaps the most infamous recall case on record".
