Patients with pulmonary embolism are at risk for death, recurrence of embolism or chronic morbidity. Appropriate treatment can reduce the incidence of all. The mortality attributable to pulmonary embolism can be up to 30% in untreated patients, more than 10 times the annual mortality for patients treated with anticoagulant drugs (2.5%). Balanced against the danger of non-treatment are the risks of treatment.

As the primary process leading to pulmonary embolism is deep venous thrombosis (DVT), antithrombotic regimens are the mainstay of treatment. These include drugs that inhibit blood coagulation (heparin, oral anticoagulants, direct thrombin inhibitors), and thrombolytic drugs. Anticoagulation, by preventing clot propagation, allows endogenous fibrinolytic activity to dissolve existing thromboemboli. Anticoagulant treatment is essentially prophylactic, since these agents only interrupt progression of the thrombotic process; unlike thrombolytic agents, they do not actively resolve it. Direct mechanical resolution of the pulmonary vascular obstruction caused by pulmonary embolism can be performed by surgical embolectomy or catheter techniques.

Unfractionated heparin (UFH), low molecular weight heparin (LMWH), direct thrombin inhibitors, and thrombolytic agents in appropriate doses, as well as surgical or catheter embolectomy, are used to treat acute pulmonary embolism. Oral anticoagulants, dextran, physical techniques that counteract venous stasis, inferior vena caval procedures, and lower doses of UFH or LMWH are used for prevention, but these prophylactic regimens are not appropriate for treatment of acute disease.

A general scheme for the treatment of pulmonary embolism is shown in fig 1. When there is a suspicion of pulmonary embolism and no strong contraindication to heparin it is wise to start treatment with a bolus of 5000–10000 U while the diagnostic work up is pursued. If subsequent tests rule out the diagnosis then heparin can be stopped. With established diagnosis, the treatment depends on the circulatory state of the patient. With severely impaired circulation—that is, …