Back in January of 2000, the manufacturer St. Jude voluntarily recalled its Silzone mechanical heart valves. St. Jude did not think it necessary for patients to undergo surgery to replace the valves. There were 36,000 Silzone valves implanted through out the world, with hundreds implanted into patients in the Atlanta Metropolitan area.
Mechanically, the St. Jude valves were seemingly all right. Therefore, the problem was not with the functioning ability of the valve but the problem was with the coating on areas of the valve. Silver was used in the making of the Silzone so to lessen the chance of infection. However, the silver reportedly leaked, which could have caused heart failure.
Additionally, in a trial called the Artificial Valve Endocarditis Reduction Trial (AVERT) an increased risk of stroke was reported. Though the chance of stroke is relatively low, the study did find a higher incidence of paravalvular leakage in patients with the valve implant.