Acute Reversible Bioprosthetic Mitral Valve Stenosis Caused by Heparin-Induced Thrombocytopenia

A 60-year-old woman with a 17-year-old prosthetic tiltingdisc mitral valve (MV) and chronic atrial fibrillation underwent emergency redo MV replacement for a stuck valve with a bioprosthetic valve (Medtronic Mosaic 27). Trans-esophageal echocardiography (TEE) on the fourth postoper-ative day showed a normal bioprosthetic valve. On the sixth postoperative day while the patient was still on intravenous heparin, her platelet count dropped to 63 000/L and a heparin-induced thrombocytopenia (HIT) antibody assay was positive. Heparin was stopped, and the patient was treated with intravenous danaparoid sodium, a factor Xa inhibitor. Oral warfarin was started when thrombocytopenia resolved. The patient was in respiratory failure and could not be weaned off the ventilator. Contrast-enhanced computed to-mography on the 14th postoperative day was negative for pulmonary emboli. However, large thrombi lining the lef