 Acute exacerbation of heart failure symptoms is a common emergency department ED presentation and is known as acute decompensated heart failure adHF. Acute decompensated heart failure represents the single greatest cost to the US hospitals funded by Medicaid. In Hong Kong HK, the incidence rate of heart failure was 3-3.81000year rising to 201000year in women over the age of 85 years in recent years. It has been estimated that 7 of all acute medical admissions was due to this condition. In recent years there has been a 10 annual increase in admissions for patients with adHF. Currently in Hong Kong, the vast majority of ED patients with adHF are admitted as inpatients to hospital. In 2005, an audit of outcomes in patients with acute cardiogenic pulmonary oedema, the most severe manifestation of heart failure, presenting to the emergency department at the Prince of Wales Hospital showed that nearly 30 of patients die within 30 days, and a further 30 require readmission within 30 days. Recent evidence from the USA suggests that ED operated observation units are effective in managing low to medium risk adHF patients, reducing length of stay LOS for these patients without adversely affecting readmission rate, morbidity and mortality. 