A mechanical prosthetic heart valve can become acutely obstructed despite anticoagulation therapy. This can be a life-threatening complication. We report the case of a 38-year-old woman who survived obstruction of her Sorin prosthetic mitral valve. She was admitted to the hospital because of severe pulmonary edema. On auscultation, mechanical valve sounds were absent. Transthoracic echocardiography showed an immobile mechanical valve. The patient suffered a cardiac arrest while being prepared for surgery, but she underwent successful mitral valve replacement after cardiopulmonary resuscitation. When patients with prosthetic mitral valves present with acute dyspnea, the possibility of an obstructed prosthetic valve must be considered in the differential diagnosis.