The Journal of Thoracic and Cardiovascular Surgery, Vol 96, 448-453, Copyright © 1988 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Late strut fracture of the Beall model 105 disc valve prosthesis
MD Silver, PR Torok, RP Slinger and T Reif
Department of Pathology, Toronto General Hospital, Ontario, Canada.
Strut fracture, with embolization of the disc occluder, caused the death of
a 64-year-old man who had a Beall model 105 heart valve prosthesis in the
mitral position for 13 years. Scanning electron microscopy of the fractured
surface revealed evidence of a fatigue failure mechanism in the metal wire.
The case is unique in that strut fractures affecting this prosthesis had
only been observed previously in the range of 141 to 342 days after
implantation. Morphological changes in this valve prompted reexamination of
three other model 105 prostheses that had been recovered from the mitral
area at necropsy or surgery 9 to 10 years after insertion in 1972 or 1973.
All had been kept in dry storage. The three prostheses and the valve
described above showed previously unrecognized cracks in the pyrolytic
carbon coating of the struts, which form the cage that limits occluder
movement. The defects were located at or near the base of struts, where
they entered the sewing ring and were bent to pass into the strut
supporting ring. We believe that the cracks in the carbon coating precede
total strut fracture and postulate that they are needed for the metal wire
to be subject to a fatigue failure mechanism.
