Chronic heart failure is a common and complex clinical syndrome that results from impaired cardiac relaxation or contraction. Patients with chronic heart failure may experience multiple debilitating symptoms, such as fatigue, pain, and peripheral oedema. However, breathlessness may be considered the most debilitating symptom. This is the first of two articles on chronic heart failure, and outlines the pathophysiology of the condition, its causes, assessment, and signs and symptoms. Part 2 will discuss the treatment and management of the condition, including pharmacological strategies, device implantation, lifestyle modification, cardiac rehabilitation and palliative care.