EXCLAIM:Extended Prophylaxis for Venous ThromboEmbolism (VTE) in Acutely Ill Medical Patients With Prolonged Immobilization

Inclusion criteria: * Recent immobilization ≤ 3 days * Level 1 mobility patients who are ≥ 40 years of age with acute medical illness or acute exacerbation of chronic medical illness * Level 2 mobility patients who * are \>75 yrs of age * are ≥ 40 years of age and have a history of VTE (deep venous thrombosis or pulmonary embolism) * are ≥ 40 years of age and have a baseline diagnosis of cancer (active cancer or history of cancer) Anticipated decreased level of mobility of 5 ± 2 days with a level of activity 1 and 2 at the time of study entry and likely to continue at a lower than pre-morbid activity level after the initial 5 ± 2 day period. PATIENTS DO NOT HAVE TO BE HOSPITALIZED IN ORDER TO BE INCLUDED IN THE STUDY.(Definition of decreased level of mobility: \_Level 1:bed rest or sedentary patients \_Level 2:level 1 with bathroom privileges) * Presence of at least one of the following medical conditions: * Heart Failure, NYHA class III and IV * Class III : Patients with cardiac disease resulting in marked limitation of physical activity. They are comfortable at rest. Less than ordinary physical activity causes fatigue, palpitationdyspnea, or anginal pain. * Class IV : Patients with cardiac disease resulting in inability to carry on any physical activity without discomfort. Symptoms of cardiac insufficiency or of the anginal syndrome may be present even at rest. If any physical activity is undertaken, discomfort is increased. * Acute respiratory insufficiency * Other acute medical conditions such as: * Acute ischemic stroke, any territory, with an appropriate neuroradiologic (head CT scan or brain MRI scan) providing results consistent with non hemorrhagic stroke * acute infection without septic shock * acute rheumatic disorders * active episode of inflammatory bowel disease * active cancer defined as history of histologically or cytologically confirmed cancer in patients who are not candidates for debulking or curative intent surgery at study entry * Any other acute medical illness or exacerbation of chronic medical illness resulting in clinically significant reduction in mobility as compared to premorbid level. Exclusion criteria: * Women who are breastfeeding, pregnant or of childbearing age and not using medically acceptable effective contraception * Patients with any evidence of an active bleeding disorder * Contraindication to anticoagulation * Major surgery within the previous 3 months * Patients who have had spinal or epidural analgesia or lumbar puncture within the preceding 24 hours * Known hypersensitivity to heparin, or LMWH, or pork derived products * A documented previous episode of heparin-induced or LMWH induced thrombocytopenia and/or thrombosis (HIT, HAT, or HITTS) * Patients who have taken part in another clinical trial within the previous thirty days * Patients with a persistent renal failure. The patient's creatinine level must be less than the creatinine level per gender/age/weight. This will replace the calculated creatinine clearance * Known or suspected severe anemia of unexplained cause considered clinically relevant by investigator * Patients with prosthetic heart valves * Patients with known cerebral metastases