Extrinsic obstruction of the Björk-Shiley valve in the mitral position

Four recently seen patients with acute, extrinsic obstruction of a Björk-Shiley prosthesis in the mitral position are described. In 2 of them, the disc occluder was stuck in the closed position by a strand of chordal tissue, which was compressed between the disc edge and valve rim. In another patient, sticking of the disc by a similar mechanism was caused by a suture that migrated into the valve orifice. Intermittent malfunction of the valve in the fourth patient was related to interference with valve opening by ventricular myocardium and occurred when the patient lay on his right side. The mechanism of extrinsic obstruction of the Björk-Shiley valve and their recognition, treatment, and prevention are discussed.