INTERBLEED: Design of an International Study of Risk Factors for Gastrointestinal Bleeding and Cardiovascular Events After Gastrointestinal Bleeding.

Background: Bleeding is the most common adverse event in those with cardiovascular (CV) disease receiving antithrombotic therapy, and it most commonly occurs in the gastrointestinal (GI) tract. Clinicians often dismiss bleeding as an adverse event that is reversible with effective antithrombotic therapy, but bleeding is associated with substantial morbidity and mortality, most likely mediated through an increased risk of CV events. Reducing the burden of bleeding requires knowledge of the potentially modifiable risk factors for bleeding and the potentially modifiable risk factors for adverse outcomes after bleeding. Methods: INTERBLEED is an international, multicentre, 2-component, observational study, with an incident case-control study examining the risk factors for GI bleeding, and a prospective cohort study of risk factors for CV events after GI bleeding. Cases either have CV disease and present to the hospital with GI bleeding or develop GI bleeding during hospitalization. Controls have CV disease, but no history of GI bleeding. We use a questionnaire to obtain detailed information on known and potential risk factors for GI bleeding and for CV events and outcomes after bleeding. We obtain CV and anthropometric measurements, perform functional and cognitive assessments, and follow participants at 3 months and 12 months. Results: As of April 1, 2022, the study is ongoing in 10 countries at 31 centres and has recruited 2407 cases and 1478 controls. Conclusions: Knowledge of risk factors for bleeding, and risk factors for CV events and functional decline after bleeding, will help develop strategies to prevent bleeding and subsequent complications.