AIMS: Hospital admission for heart failure (HF) is associated with increased mortality risk. Patients admitted with HF can be divided into those with a known previous diagnosis of HF and de novo cases. However, few studies have compared these groups. We compared long-term outcomes of patients with de novo versus acute decompensated HF (ADHF). METHODS AND RESULTS: We included data from two London hospitals, King's College Hospital and Princess Royal University Hospital. Data from all admissions were collected from the National Institute for Cardiovascular Outcomes and Research (NICOR) National Heart Failure Audit (NHFA) between 2020 and 2021. The outcome measure was all-cause mortality. A total of 561 patients were included in the study. One third (29 %) were de novo hospitalisations. Over a median follow-up of 15 (interquartile range 4-21) months, 257 (46 %) patients died. Hospitalisation for ADHF was associated with higher all-cause mortality during follow-up (51 % vs 34 %, p <
0.001). In adjusted models, hospitalisation for ADHF remained independently associated with higher all-cause mortality during follow-up (HR 0.60, 95 % CI 0.38-0.96
p = 0.03). CONCLUSION: Amongst patients hospitalised for HF, having a history of HF is associated with a higher risk of all-cause mortality than de novo cases. This may have implications for randomised studies that do not routinely document patients' HF history. Prospective studies are needed to elucidate the risk profiles of these two distinct populations for better risk stratification.