Prospective Evaluation of Dalteparin Efficacy for Prevention of VTE in Immobilized Patients Trial - PREVENT (Dalteparin)


The goal of the trial was to evaluate treatment with dalteparin compared with placebo for prevention of venous thromboembolism in hospitalized patients with acute medical illnesses.


Treatment with dalteparin would be associated with a 50% reduction in venous thromboembolic events.

Study Design

Study Design:

Patients Enrolled: 3,706
Mean Follow Up: 90 days
Mean Patient Age: Mean age 68.5 years
Female: 52

Patient Populations:

Age ≥40 years, acute medical condition requiring a projected hospitalization of ≥4 days, and had ≤3 days of prior immobilization. Possible acute medical conditions included acute congestive heart failure, acute respiratory failure that did not require ventilatory support, infection without septic shock, acute rheumatologic disorders, or inflammatory bowel disease.


Acute coronary syndrome within the previous month, a major surgical or invasive procedure performed in the previous month or to be undertaken within the next two weeks, bacterial endocarditis, immobilized lower limb because of a cast or fracture, stroke within three months, high risk of bleeding, platelet count <100x109/l, heparin or low molecular weight heparin prophylaxis given for >48 hours before randomization, contraindication to heparin anticoagulation, creatinine >2.0 mg/dl, hepatic insufficiency or active hepatitis, pregnancy or breastfeeding, or life expectancy of <1 month

Primary Endpoints:

Venous thromboembolism, defined as the combination of symptomatic deep vein thrombosis, symptomatic pulmonary embolism, and asymptomatic proximal deep vein thrombosis detected by compression ultrasound at day 21 and sudden death by day 21

Secondary Endpoints:

All-cause mortality by days 14, 21, and 90; objectively verified symptomatic deep vein thrombosis or asymptomatic proximal deep vein thrombosis at day 21; major and minor bleeding, drug-related allergic reactions, and thrombocytopenia by day 21; and symptomatic venous thromboembolism at day 90

Drug/Procedures Used:

Patients were randomized to dalteparin (5000 IU injection subcutaneously once daily for 14 days; n=1,856) or placebo (n=1,850). Treatment was continued after hospital discharge if discharge was prior to day 14. Patients were followed through 90 days.

Principal Findings:

The primary diagnosis for entry into the trial was acute heart failure (52%) and acute respiratory failure (30%). One-third of patients were ≥age 75. Baseline characteristics were similarly well-balanced between groups.

The primary endpoint of venous thromboembolism by day 21 occurred less frequently in the dalteparin group compared with placebo (2.77% vs. 4.96%, relative risk [RR] 0.55, p=0.0015), driven primarily by a lower rate of proximal, asymptomatic deep vein thrombosis (1.79% vs. 3.65%, RR 0.48). There was no difference in the secondary endpoint of all-cause mortality at 14 days, 21 days, or 90 days (6.12% vs. 6.01%, p=NS).

Symptomatic venous thromboembolism by 90-day follow-up did not differ significantly (0.93% vs. 1.33%, RR 0.70). Major bleeding trended higher in the dalteparin group than the placebo group (0.49% vs. 0.16%, p=0.15), but the overall event rate was relatively low.


Among hospitalized patients with acute medical illnesses, treatment with dalteparin was associated with a reduction in the primary endpoint of venous thromboembolism compared with placebo. Despite a high risk of venous thromboembolism in hospitalized patients, prophylaxis treatment is not widely used.

The MEDENOX trial is another large-scale, randomized trial of prophylaxis therapy for venous thromboembolism with a low molecular weight heparin, but the trial enrolled higher risk patients. The MEDENOX trial also showed a reduction in venous thromboembolism in the low molecular weight heparin arm.


Leizorovicz A, Cohen AT, Turpie AG, Olsson CG, Vaitkus PT, Goldhaber SZ. Randomized, Placebo-Controlled Trial of Dalteparin for the Prevention of Venous Thromboembolism in Acutely Ill Medical Patients. Circulation 2004;110:874-9.

Clinical Topics: Anticoagulation Management, Diabetes and Cardiometabolic Disease, Heart Failure and Cardiomyopathies, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Anticoagulation Management and Venothromboembolism, Acute Heart Failure

Keywords: Shock, Septic, Risk, Follow-Up Studies, Inflammatory Bowel Diseases, Heart Failure, Venous Thromboembolism, Dalteparin, Respiratory Insufficiency, Venous Thrombosis

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