General considerations in planning therapy of heart failure include identification of the cause, rapidity of onset, and the age of the patient. Neonates and young infants with acute onset heart failure frequently develop acidaemia, respiratory compromise or failure, and metabolic derangements such as hypoglycaemia, hypocalcaemia or hypomagnesaemia. These complications require early recognition and urgent therapy. The diagnosis of heart failure in neonates with ductal dependent congenital cardiac lesions (such as coarctation of the aorta, hypoplastic left heart syndrome or pulmonary valve atresia) allows the early institution of alprostadil (prostaglandin E1) therapy to maintain patency of the ductus arteriosus, which stabilises these infants before surgical therapy. Classic therapy for infants with heart failure due to a large left-to-right shunt consists of salt restriction, diuretics and digoxin. If this treatment is inadequate an angiotensin converting enzyme (ACE) inhibitor (e.g. captopril) is added to therapy. The question then arises whether captopril and diuretics should be the initial therapy and digoxin added if this treatment fails. Acute heart failure may occur in the immediate postoperative period after cardiac surgery or may complicate acute overwhelming infections. Therapy consists of volume loading, vasodilator or inotropic agents. Heart failure due to various forms of chronic dilated cardiomyopathy usually responds to treatment with salt restriction, diuretics, digoxin and captopril. Acute deterioration requires treatment with vasodilators and/or inotropic agents. Heart failure in fetuses may occur from sustained supraventricular tachyarrhythmias, and may respond to treatment of the mother with antiarrhythmic agents such as digoxin or procainamide.