Valve Thrombosis : Valve thrombosis causes sudden deterioration of the patient's haemodyarnics. A stuck valve may produce both stenosis and incompetence. If diagnosed early some of them could be managed by thrombolysis. Clinically it's diagnosed by the muffling of the prosthetic sounds and occurrence of new murmur. Diagnosis is confiied by echocardiography. Urgent surgery is required in these cases. Under cardio pulmonary bypass thrombectomy and clearing of the whole valve has to be done. If it is not possible to clear the inaccessible parts of the valve, it will have to be replaced. One of the advantages of bileaflet valve is that even when one leaflet is stuck the other one will be able to maintain reasonably good haemodynarnics. This helps the surgeon to perform a semi-elective operation.