Global Trends and Variation in Initial Anticoagulation of Patients Hospitalized With Acute Pulmonary Embolism

A recent U.S. study of initial anticoagulation in adults with acute pulmonary embolism (PE) requiring hospitalization found excessive intravenous unfractionated heparin (UFH) use (>50%). This deviates from society guidelines which recommend low molecular weight heparin (LMWH) for hemodynamically stable patients, except those with severe renal failure. Recent use patterns of initial anticoagulation in other countries are unclear. This study used an international registry to analyze global temporal trends in initial anticoagulation for patients with acute PE requiring hospitalization and anticoagulation variation by patient characteristics and geographic regions.

We analyzed data from the Registro Informatizado de Enfermedad TromboEmbólica (RIETE), an ongoing prospective multinational registry of consecutive patients with objectively confirmed venous thromboembolism. This study included adults hospitalized for acute symptomatic PE from January 1, 2013, through December 31, 2024, in 273 hospitals across 31 countries. We assessed temporal trends in anticoagulation selection across geographic regions. Using multivariable regression, we identified variables independently associated with UFH use.

Among 36,210 adults, the most prevalent anticoagulants administered were subcutaneous LMWH (83.2%), UFH (7.1%), and direct oral anticoagulants (6.8%). Over 12 years, LMWH use decreased slightly (85.8% to 79.2%), while UFH increased (8.9% to 10.4%). The rise in UFH from 2020 to 2024 (4.9% to 10.4%) paralleled increased reperfusion therapies (3.1% to 7.4%). Wide geographic variation was observed in LMWH (37% to 95%) and UFH use (2% to 39%). Male sex, increased weight, bleeding risk variables, abnormal vital signs, and decreased renal function were positively associated, whereas age >80 years, chronic lung disease, and prior ischemic stroke were negatively associated with UFH. Compared with Spanish hospitals, management in other European countries, the U.S., and Asia was independently associated with UFH use.

UFH use was more common in patients with higher PE severity, impaired renal function, and bleeding risk but also varied substantially by geographic location, independent of patient-level characteristics. This highlights an opportunity for some regions to align initial anticoagulation more closely with evidence-based guidelines.