Current management of intermediate- and high-risk pulmonary embolism is primarily based on curative subcutaneous or intravenous anticoagulation, with or without systemic fibrinolytic therapy or thrombectomy (8). Initial treatment with low-molecular-weight heparin (LMWH) or fondaparinux is preferred over unfractionated heparin (UFH) due to their lower risk of serious bleeding and heparin-induced thrombocytopenia (HIT) (9). UFH treatment is reserved for patients at risk of hemodynamic instability, renal failure with a GFR \< 30 ml/min, or obesity (8). Biological monitoring of anticoagulation efficacy can be performed by measuring the activated partial thromboplastin time (aPTT), as recommended by the European Society of Cardiology (ESC), or by measuring the antiXa activity of heparin, which has been shown to be beneficial in numerous studies (10,11,12). It is generally accepted that this anticoagulation should be initiated at a curative dose as early as possible (8), as this reduces in-hospital mortality and 30-day mortality (13). However, few studies have examined the impact of the time to achieve effective anticoagulation, and those that have done so have only done so in patients with high-risk pulmonary embolism (14) or have based their anticoagulation monitoring on aPTT and not on antiXa activity (13). The proposed study aims to evaluate the time to obtain effective anticoagulation and its impact on mortality, thromboembolic recurrence and the occurrence of serious bleeding in patients with clinically significant pulmonary embolism, hospitalized in an intensive care unit as well as the factors that may influence this time. It will also allow to compare the practices of the studied center in terms of initial anticoagulation dose delivered, the initiation or not of a bolus and methods of monitoring anticoagulation with the literature in order to allow an improvement in patient care.