Oral factor Xa inhibitors are widely used for the prevention of cardioembolic events in patients with atrial fibrillation and for the treatment of venous thromboembolism, thanks to their good efficacy/safety ratio compared to vitamin K antagonists. However, major bleeding remains a potentially life-threatening event, a relevant complication and real-world treatments are still heterogeneous and there are limited data available in the literature.It is therefore considered particularly important to collect and analyze information on how major bleeding complications are treated in clinical practice and to examine the outcomes.

The objective of this study is to implement a prospective, computerized collection of clinical information, as a basis for identifying and analysing patient characteristics and treatment methods for major acute bleeding events occurring during anticoagulation with oral FXa inhibitors (apixaban, edoxaban, rivaroxaban) documenting the short-term clinical outcomes and those 3 months (90 days) after the acute event.

The main questions the study aims to answer are:

• What are the severe clinical outcomes for these patients, specifically the composite incidence of death, the need for Intensive Care Unit (ICU) admission, or the need for bleeding-related rescue surgery?
• What are the characteristics of the patients experiencing these events, and how are these bleeding complications managed in real-world clinical practice? Because this is an observational study, there are no experimental pharmacological interventions. Participants will receive standard clinical care based on the normal practice of each participating hospital. Data will be evaluated during the acute hospitalization phase and at a 3-month (90 days) follow-up after the initial event The study is coordinated by FADOI (Italian Society of Hospital Internal Medicine) in collaboration with AIGO (Italian Association of Hospital Gastroenterologists and Digestive Endoscopists), AII-ISA (Italian Stroke Association) and SIMEU (Italian Society of Emergency Medicine); for this the study involves not fewer than 500 consecutive patients hospitalized in Internal Medicine, Gastroenterology, Neurology and Emergency Medicine in 50 hospital centers distributed throughout Italy.

This is a prospective, observational, multicentre, pharmacological, collaborative study. Information will be collected on patients experiencing major acute bleeding events, with details of the treatment given and the clinical outcome, both in the acute phase and 3 months (90 days) after the index event. Given the observational nature of the study, there are no indications regarding the type of patients' management and/or treatment to be performed. However, major bleeding remains a relevant complication and real-world treatments are still heterogeneous and this study aims to prospectively collect data on the management of these events, including the use of available therapies.