Twenty patients enrolled in PE group were those who admitted in hospital during 2007, with 11 males and 9 females, averaged 70(±14) years of age(44-89 years old). ALL patients were diagnosed as PE in accordance with at least 2 of following criteria. 1)Selective pulmonary arteriography showed filling defect or blockage; 2) Pulmonary ventilation perfusion scanning exhibited single or multiple blood flow perfusion defect with normal or abnormal ventilation, mismatched ratio of ventilation/perfusion; 3) Other clinical characteristics including typical manifestation of PE, arterial blood gas analysis, D-dimer test, ultrasoundcardiogram (UCG) and chest computerized tomography (CT) supported the diagnosis and excluded other cardiac and pulmonary disorders. Twenty patients with ischemic heart disease admitted at same period, excluding PE, DVT and other congenital bleeding and thrombosis diseases with comparative clinical presentation (11 males, 9 females, 44-91 years old with mean age 72±14) were enrolled in control group. The study protocol was approved by local ethics committee and informed consent was obtained from all patients in accordance with the declaration of Helsinki.