Pulmonary Embolism International THrOmbolysis Study-3

In patients with intermediate-risk pulmonary embolism, full-dose thrombolytic treatment was associated with a reduction in the combined risk of hemodynamic instability or death but was also associated with an increased risk of major and intracranial bleeding. Previous studies suggest that reduced dose of thrombolytic treatment may be as effective as the full dosage, but with a decreased risk of life-threatening bleeding. In this study, we will assess the efficacy and safety of a reduced dosage of thrombolytic therapy in patients with intermediate-high-risk acute pulmonary embolism.

The study is a randomized, placebo-controlled, double blind, multicenter, multinational trial with long-term follow-up.

Patients fulfilling the inclusion criteria and without any of the exclusion criteria will be randomized within 6 hours after the investigator had confirmed the diagnosis.

Patients will receive:

* Alteplase (if randomized in the experimental group) or placebo (if randomized in the reference group) given within 30 minutes of randomization as a 15 min intravenous infusion at a dosage of 0.6 mg/kg with a total dose not exceeding 50 mg. * Parenteral anticoagulation with low molecular weight heparin, unfractionnated heparin or fondaparinux

Primary objective is to assess the efficacy of reduced dose thrombolytic therapy in patients with acute intermediate-high-risk pulmonary embolism at day 30.

Secondary objectives are:

1. To assess the safety of reduced dose thrombolytic therapy in patients with intermediate-high-risk acute pulmonary embolism at day 30 2. To assess the net clinical benefit of reduced dose thrombolytic therapy in patients with intermediate-high-risk acute pulmonary embolism at day 30 3. To assess the effect of reduced dose thrombolytic therapy on overall mortality of patients with intermediate-high-risk acute pulmonary embolism at day 30 4. To assess the effect of reduced dose thrombolytic therapy on long-term mortality, functional impairment, residual right ventricular dysfunction and chronic thromboembolic pulmonary hypertension at 6 months and 2 years 5. To assess the effect of reduced-dose thrombolytic therapy on utilization of health care resources at day 30 and day 180