Acute heart failure (AHF) is a leading cause of hospital admission in the UK and is associated with significant mortality. The National Institute for Health and Care Excellence (2014) has published guidelines for the management of AHF but, after a clinical event in which a patient’s management differed from that recommended in the guidelines occurred in the author’s emergency department, he conducted a critical analysis of them. This article provides a case study of the clinical event, reviews the treatment methods adopted and explores the rationale for taking a different approach from that recommended in the guidelines. The evidence base for the use of diuretics, nitrates and non-invasive ventilation in the management of patients with AHF is also appraised.