The purpose of this randomized clinical trial is to determine whether outpatient treatment is as effective and safe as inpatient treatment among low-risk patients with pulmonary embolism.

Pulmonary embolism (PE) is a worldwide health problem, with an estimated incidence of up to 69 cases per 100,000 persons annually. In the U.S., 101,000 patients were hospitalized with a primary diagnosis of PE in 2002, resulting in direct medical costs of $720 million. There is growing evidence that outpatient treatment with low-molecular-weight heparin (LMWH) is an effective and safe option for up to 50% of patients with non-massive PE. Despite this evidence, outpatient treatment of PE is uncommon because (1) explicit criteria that identify patients who are at low-risk of adverse medical outcomes have not been available, and (2) randomized trials demonstrating the effectiveness and safety of outpatient treatment have not been performed. We developed a clinical prognostic model that accurately identifies patients with PE who are at low-risk for short-term mortality, symptomatic recurrent venous thromboembolism (VTE), and major bleeding. This model provides clinicians an easily applied, explicit risk stratification tool for patients with PE, addressing a key barrier to outpatient treatment. The broad objective of this clinical trial is to address the other major barrier to outpatient treatment of low-risk patients with non-massive PE, the effectiveness and safety of outpatient management. We will randomize low-risk patients (identified using our prognostic model) with PE from hospital emergency departments to receive outpatient or inpatient treatment with LMWH for ≥5 days, followed by oral anticoagulation. The specific aims of the project are to compare (1) the frequency of recurrent VTE, (2) the frequency of major bleeding and all-cause mortality, and (3) medical resource utilization and patient satisfaction with care among patients randomized to receive outpatient or inpatient treatment with LMWH. The primary study outcome will be the rate of symptomatic recurrent VTE at 3 months after randomization. The secondary outcomes will be the rate of major bleeding and all-cause mortality. The ancillary outcomes will be medical resource utilization and patient satisfaction with care. The hypotheses guiding this trial are that outpatient treatment with LMWH is as effective and safe as inpatient treatment with LMWH, and is also associated with reduced medical resource utilization and increase patient satisfaction with care. This study is innovative because it translates a validated prognostic model into clinical practice and represents the first direct comparison of outpatient versus inpatient treatment of low-risk patients with PE. Successful completion of this project will provide a strong scientific basis for treating low-risk patients with PE in the outpatient setting. Outpatient management of low-risk patients with PE is likely to improve quality and efficiency of care by reducing resource utilization and increasing patient satisfaction with care. Our findings will have importance to physicians, hospitals, and policy-makers who are committed to optimizing patient safety and providing high-quality, cost-effective care.

Inclusion Criteria:

• age >18 years
• objectively confirmed diagnosis of pulmonary embolism
• patients at low-risk (Pulmonary Embolism Severity Index score <=85)

Exclusion Criteria:

• patients at high-risk (Pulmonary Embolism Severity Index score >85)
• presence of hypoxemia (arterial SO2 <90% measured by pulse oximetry or an paO2 on room air of <60 mm Hg measured by blood gas analysis)
• systolic blood pressure of <100 mm Hg
• chest pain necessitating parenteral opioid administration
• active bleeding or at high-risk of major bleeding (stroke during the preceding 10 days, gastrointestinal bleeding during the preceding 14 days, or platelets <75,000 per mm3)
• renal failure (creatinine clearance of <30 ml/minute based on the Cockcroft-Gault formula)
• body mass >150 kg
• history of HIT or allergy to heparins
• therapeutic oral anticoagulation (INR ≥2)at the time of pulmonary embolism diagnosis
• potential barriers to treatment adherence or follow-up (alcoholism, illicit current or recent drug use, psychosis, dementia, homelessness, lack of telephone access, transportation time to nearest ED >45 minutes)
• known pregnancy
• imprisonment
• diagnosis of pulmonary embolism >23 hours ago
• refusal or inability to provide informed consent
• prior enrollment in the study