One hundred and eighty two consecutive in-hospital patients with 220 episodes of PVT between 1993 and 2009 were included in the study. The patients were enrolled after informed consent if there was no contraindication, to thrombolysis. The study was approved by the local Ethics Board. The patient demographics, past medical history, date of the operation, type and make of the prosthetic valve, rhythm disorders, aspirin use, NYHA functional capacity, leading symptoms and international normalization ratio (INR) values at the time of admission were prospectively entered into a database.The diagnosis of PVT was verified each time by transesophageal echocardiography (TEE) when a patient was admitted with thromboembolism or persistently low INR for the preceding consecutive 3 months and when a transthoracic echocardiography (TTE) documented prosthetic valve dysfunction or thrombus. All patients underwent TTE and TEE examination before and after the thrombolysis sessions. The cross sectional area and the longest diameter of the thrombus were measured on TEE recordings