***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Extended- duration low-molecular-weight heparin has been shown to prevent venous thromboembolism ( VTE ) in high-risk surgical patients . OBJECTIVE To evaluate the efficacy and safety of extended- duration enoxaparin thromboprophylaxis in acutely ill medical patients . DESIGN R and omized , parallel , placebo-controlled trial . R and omization was computer-generated . Allocation was central ized . Patients , caregivers , and outcome assessors were blinded to group assignment . ( Clinical Trials.gov registration number : NCT00077753 ) SETTING : 370 sites in 20 countries across North and South America , Europe , and Asia . PATIENTS Acutely ill medical patients 40 years or older with recently reduced mobility ( bed rest or sedentary without [ level 1 ] or with [ level 2 ] bathroom privileges ) . Eligibility criteria for patients with level 2 immobility were amended to include only those who had additional VTE risk factors ( age > 75 years , history of VTE , or active or previous cancer ) after interim analyses suggested lower-than-expected VTE rates . INTERVENTION Enoxaparin , 40 mg/d subcutaneously ( 2975 patients ) , or placebo ( 2988 patients ) , for 28 + /- 4 days after receiving open-label enoxaparin for an initial 10 + /- 4 days . MEASUREMENTS Incidence of VTE up to day 28 and of major bleeding events up to 48 hours after the last study treatment dose . RESULTS Extended- duration enoxaparin reduced VTE incidence compared with placebo ( 2.5 % vs. 4 % ; absolute risk difference favoring enoxaparin , -1.53 % [ 95.8 % CI , -2.54 % to -0.52 % ] ) . Enoxaparin increased major bleeding events ( 0.8 % vs. 0.3 % ; absolute risk difference favoring placebo , 0.51 % [ 95 % CI , 0.12 % to 0.89 % ] ) . The benefits of extended- duration enoxaparin seemed to be restricted to women , patients older than 75 years , and those with level 1 immobility . LIMITATION Estimates of efficacy and safety for the overall trial population are difficult to interpret because of the change in eligibility criteria during the trial . CONCLUSION Use of extended- duration enoxaparin reduces VTE more than it increases major bleeding events in acutely ill medical patients with level 1 immobility , those older than 75 years , and women . PRIMARY FUNDING SOURCE Sanofi-aventis Betrixaban is an oral direct inhibitor of factor Xa ( FXa ) being developed for the prevention of venous thromboembolism ( VTE ) . Its antithrombotic effects had not been previously tested in patients . This exploratory clinical trial in the US and Canada r and omized 215 patients undergoing elective total knee replacement ( TKR ) in a 2:2:1 ratio to receive post-operative betrixaban 15 mg or 40 mg p.o . bid or enoxaparin 30 mg s.c . q12h , respectively , for 10 - 14 days . The betrixaban dosage was blinded , but enoxaparin was not . Primary efficacy outcome was the incidence of VTE , consisting of deep-vein thrombosis ( DVT ) on m and atory unilateral ( operated leg ) venography , symptomatic proximal DVT , or pulmonary embolism ( PE ) through Day 10 - 14 . Safety outcomes included major and clinical ly significant non-major bleeds through 48 h after treatment . All efficacy and bleeding outcomes were adjudicated by a blinded independent central adjudication committee . Of 214 treated patients , 175 ( 82 % ) were evaluable for primary efficacy . VTE incidence was 14/70 ( 20 % ; 95 % CI : 11 , 31 ) for betrixaban 15 mg , 10/65 ( 15 % ; 95 % CI : 8 , 27 ) for betrixaban 40 mg , and 4/40 ( 10 % ; 95 % CI : 3 , 24 ) for enoxaparin .  No bleeds were reported for betrixaban 15 mg , 2 ( 2.4 % ) clinical ly significant non-major bleeds with betrixaban 40 mg , and one ( 2.3 % ) major and two ( 4.6 % ) clinical ly significant non-major bleeds with enoxaparin . A dose- and concentration-dependent effect of betrixaban  on inhibition of thrombin generation and anti-Xa levels was observed . Betrixaban demonstrated antithrombotic activity and appeared well tolerated in knee replacement patients at the doses studied BACKGROUND The efficacy and safety of prolonging prophylaxis for venous thromboembolism in medically ill patients beyond hospital discharge remain uncertain . We hypothesized that extended prophylaxis with apixaban would be safe and more effective than short-term prophylaxis with enoxaparin . METHODS In this double-blind , double-dummy , placebo-controlled trial , we r and omly assigned acutely ill patients who had congestive heart failure or respiratory failure or other medical disorders and at least one additional risk factor for venous thromboembolism and who were hospitalized with an expected stay of at least 3 days to receive apixaban , administered orally at a dose of 2.5 mg twice daily for 30 days , or  enoxaparin , administered subcutaneously at a dose of 40 mg once daily for 6 to 14 days . The primary efficacy outcome was the 30-day composite of death related to venous thromboembolism , pulmonary embolism , symptomatic deep-vein thrombosis , or asymptomatic proximal-leg deep-vein thrombosis , as detected with the use of systematic bilateral compression ultrasonography on day 30 . The primary safety outcome was bleeding . All efficacy and safety outcomes were independently adjudicated . RESULTS A total of 6528 subjects underwent r and omization , 4495 of whom could be evaluated for the primary efficacy outcome --2211 in the apixaban group and 2284 in the enoxaparin group . Among the patients who could be evaluated , 2.71 % in the apixaban group ( 60 patients ) and 3.06 % in the enoxaparin group ( 70 patients ) met the criteria for the primary efficacy outcome ( relative risk with apixaban , 0.87 ; 95 % confidence interval [ CI ] , 0.62 to 1.23 ; P=0.44 ) . By day 30 , major bleeding had occurred in 0.47 % of the patients in the apixaban group ( 15 of 3184 patients ) and in 0.19 % of the patients in the enoxaparin group ( 6 of 3217 patients ) ( relative risk , 2.58 ; 95 % CI , 1.02 to 7.24 ; P=0.04 ) . CONCLUSIONS In medically ill patients , an extended course of thromboprophylaxis with apixaban was not superior to a shorter course with enoxaparin . Apixaban was associated with significantly more major bleeding events than was enoxaparin . ( Funded by Bristol-Myers Squibb and Pfizer ; Clinical Trials.gov number , NCT00457002 . ) This study aim ed to determine the frequency of fatal pulmonary emboli in hospitalised medical patients by a retrospective necropsy review and prospect i ve non-interventional patient follow up study . The main outcome measure , necropsy proven fatal pulmonary embolism , was determined from 400 consecutive necropsy records and 200 consecutive medical inpatient episodes .  Fatal pulmonary embolism was recorded in 29 of 400 necropsies ; 17 were medical patients . Thirty one of 200 consecutive medical patients died . Fourteen necropsies were performed and revealed pulmonary embolism as the cause of death in five patients . The incidence of necropsy proven fatal pulmonary embolism was therefore 2.5 % ( 95 % confidence intervals 0.8 % to 5.7 % ) . Therefore , one in 40 medical patients had pulmonary embolism recorded as the cause of death at necropsy . As the necropsy rate was only 45 % the incidence of fatal pulmonary embolism may be greater . There is , therefore , a need to perform more large prospect i ve studies to confirm the incidence of fatal pulmonary embolism in medical patients and to identify risk factors and effective antithrombotic prophylaxis BACKGROUND Hospitalized patients with medical illness are especially susceptible to the development of venous thromboembolism ( VTE ) . METHODS To improve our underst and ing of the demographics , comorbidities , risk factors , clinical presentation , prophylaxis , and treatment of hospitalized medical patients with deep vein thrombosis ( DVT ) , we evaluated hospitalized medical patients in a prospect i ve registry of 5,451 consecutive ultrasound-confirmed DVT patients at 183 institutions in the United States . RESULTS Of those patients who participated in the registry , 2,609 ( 48 % ) were hospitalized medical patients . Compared with 1,953 hospitalized nonmedical patients with DVT , medical patients with DVT experienced pulmonary embolism ( PE ) more often ( 22.2 % vs 15.5 % , respectively ; p < 0.0001 ) . However , medical patients in whom DVT developed had received  VTE prophylaxis far less frequently than nonmedical patients ( 25.4 % vs 53.8 % , respectively ; p < 0.0001 ) . The underutilization of  VTE prophylaxis  among hospitalized medical patients extended to both pharmacologic and mechanical modalities . In a multivariable logistic regression analysis of all hospitalized VTE patients , status as a medical patient was negatively associated with receiving prophylaxis ( adjusted odds ratio , 0.47 ; 95 % confidence interval , 0.28 to 0.78 ) . CONCLUSIONS Hospitalized medical patients face " double trouble . " First , during hospitalization for a reason other than VTE , VTE prophylaxis is omitted in medical patients more often than in nonmedical patients . Second , when VTE develops as a complication of hospitalization , hospitalized medical patients experience PE more often . Further studies should focus on underst and ing why prophylaxis is often omitted in hospitalized medical patients and on improving its implementation in this vulnerable population PURPOSE The purpose of this investigation is to estimate the prevalence of  acute pulmonary embolism ( PE ) in a general hospital , its frequency among patients who died , and the ability of physicians to diagnose PE antemortem . METHODS The prevalence of acute PE among 51,645 patients hospitalized over a 21-month period was assessed in 1 of the 6 clinical centers ( Henry Ford Hospital ) that participated in the collaborative study , prospect i ve investigation of pulmonary embolism diagnosis ( PIOPED ) . The diagnosis of PE was made by pulmonary angiography , or in those who did not undergo pulmonary angiography  because they declined or were ineligible for r and omization to angiography in PIOPED , the diagnosis was based on the ventilation/perfusion ( V/Q ) lung scan . Based on data in PIOPED , PE was considered to be present in 87 % of patients with high probability V/Q scam interpretations , 30 % with intermediate probability interpretations , 14 % with low probability interpretations , and 4 % with nearly normal V/Q scans . RESULTS The estimated prevalence of acute PE in hospitalized patients was 526 of 51,645 ( 1.0 % ; 95 % confidence interval [ CI ] , 0.9 to 1.1 % ) . Based on extrapolated data from autopsy , PE was estimated to have caused or contributed to death in 122 of 51,645 ( 0.2 % ; 95 % CI , 0.19 to 0.29 % ) . Pulmonary embolism was observed at autopsy in 59 of 404 ( 14.6 % ; 95 % CI , 11.3 to 18.4 % ) . Among patients with PE at autopsy , the PE caused or contributed to death in 22 of 59 ( 37.3 % ; 95 % CI , 25.0 to 50.9 % ) and PE was incidental in 37 of 59 ( 62.7 % ; 95 % CI , 49.1 to 75.0 % ) . Among patients at autopsy who died from PE , the diagnosis was unsuspected in 14 of 20 ( 70.0 % ; 95 % CI , 45.7 to 88.1 % ) . Most of these patients had advanced associated disease  . In these patients , death from PE occurred within 2.5 h in 13 of 14 ( 92.9 % ; 95 % CI , 66.1 to 99.8 % ) . CONCLUSION Pulmonary embolism is common in a general hospital . The prevalence of PE at autopsy has not changed over 3 decades . The frequency of unsuspected PE in patients at autopsy has not diminished . Even among patients who die from PE , the PE is usually unsuspected . Such patients , however , typically have advanced disease . Among moribund patients , incidental PE is rarely diagnosed . Patients who suffer sudden unexplained catastrophic events in the hospital are a group in whom the diagnosis might be suspected more frequently if physicians maintain a high index of suspicion 
    Output:
    
Conclusion : In acute medically ill patients , prolonged thromboprophylaxis with an oral FXa inhibitor is more protective than regular short-term treatment with enoxaparin .
However , treatment with FXa inhibitors is significantly associated with major bleeding , both in long- and short-term treatment compared with enoxaparin