Immature Plateletes in the Etiopathology of Deep Venous Thrombosis

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