BackgroundFew data regarding the prevalence and prognostic impact of mitral regurgitation (MR) in patients with worsening chronic or new-onset acute heart failure (HF) are available. We investigated the role of MR in the BIOlogy Study to TAilored Treatment in Chronic Heart Failure (BIOSTAT-CHF).Methods and resultsWe performed a retrospective post-hoc analysis including patients from both the index and validation BIOSTAT-CHF cohorts with data regarding MR status. The primary endpoint was a composite of all-cause death or HF hospitalization. Among 4023 patients included, 1653 patients (41.1%) had moderate-severe MR. Compared to others, patients with moderate-severe MR were more likely to have atrial fibrillation and chronic kidney disease and...