Acute heart failure can present as new-onset heart failure in people without known cardiac dysfunction, or as acute decompensation of chronic heart failure. Acute heart failure is a common cause of admission to hospital (over 67,000 admissions in England and Wales per year) and is the leading cause of hospital admission in people 65 years or older in the UK. This guideline includes important aspects of the diagnosis and management of acute heart failure that are not addressed by the NICE guideline on chronic heart failure. The guideline on chronic heart failure focuses on long-term management rather than on the immediate care of someone who is acutely unwell as a result of heart failure. This guideline covers the care of adults (aged 18 years or older) who have a diagnosis of acute heart failure, have possible acute heart failure, or are being investigated for acute heart failure. It includes the following key clinical areas: the role of early natriuretic peptide testing and echocardiography the role of specialist management units the use of ventilatory support, pharmacological therapy and ultrafiltration treatment after stabilisation, including selected surgical interventions and initiation of the pharmacological therapies that are used in the management of chronic heart failure. Drug recommendations The guideline will assume that prescribers will use a drug's summary of product characteristics to inform decisions made with individual patients. In memory of Christopher Jones, patient member of the GDG who ensured that the patient voice was heard during the development of this guideline. Key priorities for implementation The following recommendations have been identified as priorities for implementation. The full list of recommendations is in section 1. 