We found that among those with HFrEF, AF was associated with an increased risk of HF hospitalization or CV death and an increased risk of HF hospitalization alone; when stratified by NT-proBNP level of 1000 pg/mL, these findings persisted only among those with AF and NT-proBNP level of 1000 pg/mL and higher. Here, NPPB is linked to atrial fibrillation.