ALB and susceptibility to pneumonia measurement: This study aims to evaluate the prognostic value of the red blood cell distribution width to albumin ratio (RAR) and develop a machine learning model for predicting 31-day in-hospital mortality in HF patients with pneumonia in ICU.<h4>Methods</h4>We included the MIMIC-IV cohort and an external validation cohort from the First Affiliated Hospital of Zhengzhou University.