Ball variance and fracture of mitral valve prosthesis causing recurrent thromboemboli.

This report documents the ninth case of ball variance in a Starr-Edwards Model 6000 mitral prosthesis occurring 10 years, 9 months after implantation. It is the fourth case of fracture of a mitral ball of any type. As this case illustrates, the presence of ball variance in the mitral position may be subtle. One must carry a high index of suspicion if the diagnosis is to be made and treatment undertaken before catastrophic events take place. The incidence of ball variance is likely to increase with the length of implantation. We recommend surgical replacement of the defective prosthesis immediately upon confirmation of diagnosis.