Here is the design of a clinical trial:

Official Title: An Efficacy and Safety Study of New Oral Anticoagulants and Vitamin K Antagonists for the Anticoagulation for the Implantation of Vena Cava Filters: A Prospective Randomized Controlled Trial

Included conditions:
- Venous Thromboembolism

Study Armgroups:
- {'label': 'Rivaroxaban', 'type': 'EXPERIMENTAL', 'description': 'Participants will receive rivaroxaban 15mg oral twice daily for 3 weeks after operation, later rivaroxaban 20mg oral once daily until 3 months after the filter is retrieved.', 'interventionNames': ['Drug: Rivaroxaban']}
- {'label': 'Warfarin/ Nadroparin', 'type': 'ACTIVE_COMPARATOR', 'description': 'Participants will receive Nadroparin 1mg/kg twice daily (subcutaneous), plus warfarin 3mg oral once daily for 5 days after the operation, later warfarin(oral) at individually titrated doses(0.75mg to 18mg) to achieve a target international normalized ratio (INR) of 2.0 to 3.0, once daily until 3 months after the filter is retrieved.', 'interventionNames': ['Drug: Warfarin', 'Drug: Nadroparin']}

Interventions:
- {'type': 'DRUG', 'name': 'Rivaroxaban', 'description': '15mg twice daily for 3 weeks after operation, later 20mg once daily until 3 months after the filter is removed. Application: oral', 'armGroupLabels': ['Rivaroxaban'], 'otherNames': ['Xarelto']}
- {'type': 'DRUG', 'name': 'Warfarin', 'description': '3mg for 5 days after the operation, later 0.75mg to 18mg depending on INR (2.0-3.0) until until 3 months after the filter is removed. Frequency: once daily Application: oral', 'armGroupLabels': ['Warfarin/ Nadroparin'], 'otherNames': ['coumadin']}
- {'type': 'DRUG', 'name': 'Nadroparin', 'description': 'Dose: 1mg/kg Duration: 5 days after the operation Frequency: twice daily Application: subcutaneous', 'armGroupLabels': ['Warfarin/ Nadroparin'], 'otherNames': ['Fraxiparin']}

Primary Outcomes:
- {'measure': 'All cause mortality', 'description': 'Percentage of participants with all deaths', 'timeFrame': '4 months after the filter is retrieved'}
- {'measure': 'Pulmonary embolism related mortality', 'timeFrame': '4 months after the filter is retrieved'}
- {'measure': 'Percentage of Participants with bleeding', 'description': 'Clinically relevant bleeding is defined as a composite of major or clinically relevant nonmajor bleeding', 'timeFrame': '4 months after the filter is retrieved'}
- {'measure': 'Percentage of Participants With Symptomatic Recurrent Venous Thromboembolism', 'description': 'the Composite of Recurrent Deep Vein Thrombosis \\[DVT\\] or Fatal or Non-fatal Pulmonary Embolism \\[PE\\]', 'timeFrame': '4 months after the filter is retrieved'}

Please estimate the sample size based on the assumption: 
Power of 0.8, dropout rate of 10%
Sample size calculation
        Adverse clinical outcomes of IVC filters are defined as a composite of recurrent VTE, IVC thrombosis or death. Weinberg et al32 reported that the adverse clinical outcomes rate for patients with IVC filters and without anticoagulants was 67.9%. However, the rate was only 30.5% and 29.1% for patients receiving prophylactic or therapeutic anticoagulation, respectively. For the group design non-inferiority test, 180 cases are sufficient under a power of 0.8, and the non-inferiority margin was â0.12. Thus, we will recruit 200 patients, considering a dropout rate of 10%, 100 patients per group.