Low-molecular-weight heparin (LWMH) appears to be at least as effective and safe as standard, unfractionated heparin (UFH)for the treatment of patients with deep vein thrombosis(DVT) and may also be so in patients with pulmonary thromboembolism (PTE). Only limited data are available on the evaluation of body weight adjusted LWMH and standard UFH for the initial treatment of PTE in Chinese population. The aim of this study is to determine whether body weight-adjusted, subcutaneous Nadroparin is as effective and safe as UFH for treatment of patients with objectively documented PTE.

Low-molecular-weight heparin (LWMH) appears to be at least as effective and safe as standard, unfractionated heparin (UFH)for the treatment of patients with deep vein thrombosis(DVT) and may also be so in patients with pulmonary thromboembolism (PTE). Only limited data are available on the evaluation of body weight adjusted LWMH and standard UFH for the initial treatment of PTE in Chinese population.

The aim of this study is to determine whether body weight-adjusted, subcutaneous Nadroparin is as effective and safe as UFH for treatment of patients with objectively documented PTE.

An open-label, adjudicator-blinded, randomized controlled trial of patients with symptomatic non-massive PTE from 37 major hospitals in China is conducted . Intravenous UFH was administered received an initial bolus dose of 80 IU/kg, followed by a continuous infusion at an initial rate of 18 IU/kg /hour. The dose was subsequently adjusted by activated partial thromboplastin time (APTT) monitoring. LMWH (nadroparin) was administered subcutaneously at a dose of 86 anti-factor Xa IU/kg every 12 hours.

Both treatments were overlapped with at least 3 months of warfarin therapy. Main outcome measures were combined end point of clinical effect, image improvement,Recurrent venous thromboembolism(VTE), major bleeding, and death within 14 days and 3 months of randomization.

Inclusion Criteria:

• 18 to 75 years of age
• Symptomatic non massive PTE confirmed either by a high probability ventilation-perfusion lung scanning (V/Q scan) or by the presence of intraluminal filling defect on spiral computed tomographic pulmonary angiography (CTPA)
• Haemodynamic stabile, anatomic obstruction no more than 2 lobes on CTPA, or defect no more than 7 segments on V/Q scan,and normal right ventricular function
• Symptoms within 15 days
• Written informed consent obtained before randomization.

Exclusion Criteria:

• Unfractioned heparin anticoagulation for more than 36 hours prior enrollment,
• Massive PTE or sub-massive PTE requiring thrombolytic therapy or pulmonary embolectomy; Active bleeding or disorders contraindicating anticoagulant therapy
• Chronic thromboembolism pulmonary hypertension(CTEPH) without evidence of recent episode; Severe hepatic or renal failure
• Allergy to heparin, other components of Tinzaparin or acenocoumarol,
• Pregnant status;a life expectancy of less than 3 months;
• Previous thrombocytopenia induced by heparin
• Thrombocytopenia < 100000/mm3,