The study is designed to evaluate the role of platelets and immature platelets in the ethiopathology of deep venous thrombosis and pulmonary embolism.

Inclusion Criteria:

• Patients with a newly diagnosed deep venous thrombosis and/or pulmonary embolism. The thrombembolism is idiopathic or caused by immobilisation.
• Control: Patients that present with a suspicion of deep venous thrombosis which is excluded by duplex sonography.

Exclusion Criteria:

• therapy with glycoprotein IIb/IIIa-antagonists within the last 10 days
• therapy with antiplatelet drugs (ASA, Clopidogrel, Ticagrelor, Prasugrel, Dipyridamol)
• preexisting anticoagulation
• number of platelets < 100.000/µl
• anemia (hematocrit < 35%, Hb < 10 g/dl)
• age > 80 y or < 18 y
• renal insufficiency GFR < 30 ml/min
• hepatic impairment with an increased risk for bleeding or coagulopathy, or liver cirrhosis (≥ Child Pugh B)
• intracranial or intracerebral bleeding within the last six months
• intraspinal or intracerebral vascular anomalies
• clinically relevant acute bleedings
• malign disease
• infections within the last 7 d
• hematological, rheumatologic and autoimmune diseases
• operations within the last six months
• transfusion of rec celll concentrates within the last six months
• transfusion of fresh frozen plasma or platelet concentrates within the last month
• preexisting medication with CYP 3A4 inhibitors and inductors, p-glycoprotein inhibitors (Azol-Antimycotis, HIV protease-inhibitors)
• hypersensitivity/contraindications for Rivaroxaban
• pregnancy or lactation
• thrombophilia
• thrombocytopathy

all-comers