* patients with absolute contraindication of pharmacological thromboprophylaxis and/ anticoagulation * congenital hemorrhagic disorders * hypersensitivity to heparin * personal history of heparin-induced thrombocytopenia * active major bleeding or conditions predisposing to major bleeding. major bleeding is defined as fulfilling any one of these three criteria: a) occurs in a critical area or organ (e.g.intracranial, intraspinal, intraocular, retroperitoneal, intra-articular or pericardial, intra-uterine or intramuscular with compartment syndrome), b) causes a fall in haemoglobin level (hb) of ≥2g/dl in a 24h period, or c) leads to transfusion of 2 or more units of whole blood or red blood cells (13). * suspected or confirmed bacterial endocarditis * ongoing or planned therapeutic anticoagulation for any other indication * platelet count \<50,000/μl within the past 24 hours or hb level \<8g/dl * prothrombin time (pt) ≥2 seconds above the upper limit of age-appropriate local reference range within the past 24 hours * activated partial thromboplastin time (aptt) ≥4 seconds above the upper limit of age-appropriate local reference range within the past 24 hours * fibrinogen \<2.0 g/l * severe renal impairment (crcl\<30 ml/min) or acute kidney injury * use of dual antiplatelet therapy * pregnancy * unwillingness to consent

* patients with absolute contraindication of pharmacological thromboprophylaxis and/ anticoagulation * congenital hemorrhagic disorders * hypersensitivity to heparin * personal history of heparin-induced thrombocytopenia * active major bleeding or conditions predisposing to major bleeding. major bleeding is defined as fulfilling any one of these three criteria: a) occurs in a critical area or organ (e.g.intracranial, intraspinal, intraocular, retroperitoneal, intra-articular or pericardial, intra-uterine or intramuscular with compartment syndrome), b) causes a fall in haemoglobin level (hb) of ≥2g/dl in a 24h period, or c) leads to transfusion of 2 or more units of whole blood or red blood cells (13). * suspected or confirmed bacterial endocarditis * ongoing or planned therapeutic anticoagulation for any other indication * platelet count \<50,000/μl within the past 24 hours or hb level \<8g/dl * prothrombin time (pt) ≥2 seconds above the upper limit of age-appropriate local reference range within the past 24 hours * activated partial thromboplastin time (aptt) ≥4 seconds above the upper limit of age-appropriate local reference range within the past 24 hours * fibrinogen \<2.0 g/l * severe renal impairment (crcl\<30 ml/min) or acute kidney injury * use of dual antiplatelet therapy * pregnancy * unwillingness to consent

- patients with absolute contraindication of pharmacological thromboprophylaxis and/ anticoagulation - congenital hemorrhagic disorders - hypersensitivity to heparin - personal history of heparin-induced thrombocytopenia - active major bleeding or conditions predisposing to major bleeding. major bleeding is defined as fulfilling any one of these three criteria: a) occurs in a critical area or organ (e.g.intracranial, intraspinal, intraocular, retroperitoneal, intra-articular or pericardial, intra-uterine or intramuscular with compartment syndrome), b) causes a fall in haemoglobin level (hb) of ≥2g/dl in a 24h period, or c) leads to transfusion of 2 or more units of whole blood or red blood cells (13). - suspected or confirmed bacterial endocarditis - ongoing or planned therapeutic anticoagulation for any other indication - platelet count <50,000/μl within the past 24 hours or hb level <8g/dl - prothrombin time (pt) ≥2 seconds above the upper limit of age-appropriate local reference range within the past 24 hours - activated partial thromboplastin time (aptt) ≥4 seconds above the upper limit of age-appropriate local reference range within the past 24 hours - fibrinogen <2.0 g/l - severe renal impairment (crcl<30 ml/min) or acute kidney injury - use of dual antiplatelet therapy - pregnancy - unwillingness to consent

- patients with absolute contraindication of pharmacological thromboprophylaxis and/ anticoagulation - congenital hemorrhagic disorders - hypersensitivity to heparin - personal history of heparin-induced thrombocytopenia - active major bleeding or conditions predisposing to major bleeding. major bleeding is defined as fulfilling any one of these three criteria: a) occurs in a critical area or organ (e.g.intracranial, intraspinal, intraocular, retroperitoneal, intra-articular or pericardial, intra-uterine or intramuscular with compartment syndrome), b) causes a fall in haemoglobin level (hb) of ≥2g/dl in a 24h period, or c) leads to transfusion of 2 or more units of whole blood or red blood cells (13). - suspected or confirmed bacterial endocarditis - ongoing or planned therapeutic anticoagulation for any other indication - platelet count <50,000/μl within the past 24 hours or hb level <8g/dl - prothrombin time (pt) ≥2 seconds above the upper limit of age-appropriate local reference range within the past 24 hours - activated partial thromboplastin time (aptt) ≥4 seconds above the upper limit of age-appropriate local reference range within the past 24 hours - fibrinogen <2.0 g/l - severe renal impairment (crcl<30 ml/min) or acute kidney injury - use of dual antiplatelet therapy - pregnancy - unwillingness to consent