Here is the design of a clinical trial:

Official Title: Tinzaparin Lead-In to Prevent the Post-Thrombotic Syndrome Phase IV Pilot Study

Included conditions:
- Deep Vein Thrombosis
- Post Thrombotic Syndrome

Study Armgroups:
- {'label': 'Tinzaparin', 'type': 'EXPERIMENTAL', 'description': 'initial 3-week lead-in course of low molecular weight heparin (tinzaparin 175 units/Kg sc daily) followed by a direct oral anticoagulant (rivaroxaban 20mg po daily) for at least 3 months', 'interventionNames': ['Drug: tinzaparin']}
- {'label': 'Rivaroxaban', 'type': 'ACTIVE_COMPARATOR', 'description': 'Direct oral anticoagulant only (rivaroxaban 15mg po BID for 3 weeks followed by rivaroxaban 20mg po daily ) for at least 3 months', 'interventionNames': ['Drug: Rivaroxaban']}

Interventions:
- {'type': 'DRUG', 'name': 'tinzaparin', 'description': 'low molecular weight heparin', 'armGroupLabels': ['Tinzaparin']}
- {'type': 'DRUG', 'name': 'Rivaroxaban', 'description': 'direct oral anticoagulant', 'armGroupLabels': ['Rivaroxaban']}

Primary Outcomes:
- {'measure': 'PTS at 6 months', 'description': 'Proportion of patients with PTS at 6 months using the Villalta scale. PTS will be diagnosed using the Villalta scale. This clinical scale is the recommended standard to diagnose PTS.', 'timeFrame': '6 months post randomization'}
- {'measure': 'Main feasibility', 'description': 'Main feasibility outcomes: a. Proportion of eligible patients, among patients screened b. Proportion of recruited patients, among patients who are eligible c. Proportion of patients who are compliant with tinzaparin, among recruited patients assigned to tinzaparin arm.', 'timeFrame': '3 months post randomization'}

Please estimate the sample size based on the assumption: 
The median sample size per arm for pilot studies is 30 participants (range 8-114) and for feasibility studies is 36 (range 15-114). Temporal effects on PTS frequency are considered but not adjusted for in this pilot trial.
Sample size and power calculations
        The objective of this pilot trial is to assess feasibility of the study protocol and to obtain an estimate of the magnitude of difference in effectiveness between tinzaparin followed by rivaroxaban compared with upfront rivaroxaban. This will inform our estimation of the required sample size for a larger, definitive future trial. There are currently no available data to estimate the expected magnitude of this difference, as DOACs have not been directly compared with LMWHs for the prevention of PTS. Other PTS literature has shown effect sizes around 0.25 in terms of the effect of the intervention on the Villalta scale score at 6 months,37 suggesting that a sample size of around 25 patients per treatment arm would be sufficient.38 In an audit of sample sizes for pilot and feasibility trials undertaken in the UK, Billingham et al found that the median sample size per arm for pilot studies was 30 participants (range 8â114) and for feasibility studies was 36 (range 15â114).39 Another factor that may influence the required sample size is the temporal effect on frequency of PTS. While some authors have found that PTS frequency increases with time,40 others have not,41 suggesting that adjusting the sample size for this is premature. We plan to recruit 60 participants in total, which places our pilot trial within the recommended sample size range for pilot studies.