The diagnostic criteria of acute PE were the same as the above and the diagnosis of DVT was based on the criteria previously reported (12) . The criteria for CTEPH developed by American AHA were used for the diagnosis of CTEPH (13) . In the present study, 13 patients had the mean pulmonary artery systolic pressure of 54-106 mmHg. Malignancies, use of immunosuppresants or autoimmune diseases were excluded in all patients. All patients were from Shanghai, China. The present study was approved by the Ethics Committee of Tongji Hospital and informed consent was obtained before study.