 The objective of the study is to obtain the clinical data from patients who had the Perimount Heat Valve Type:6900P and 2900 Replacement Surgery in Guangdong General Hospital during 2001-2007 in order to evaluate the performace of this heart valve prothesis and collect the patients post-operation infomation including the current living status, mortality rate, and the possibility of re-operation,bleeding and thrombosis. 