Severe congenital heart disease is most often encountered in the neonate. However, many defects go unnoticed until later in life, frequently becoming apparent only when the animal is first put into work, or at a routine examination. Other conditions may complicate the clinical picture in animals with cardiac disease and may be more common in animals of different age. For example, foals are more likely to suffer diseases such as septicaemia and pneumonia than adults. These conditions may cause tachypnoea and tachycardia which can be mistaken for a sign of cardiac disease. In addition, clinical signs may sometimes be incorrectly attributed to heart disease in animals with incidental cardiac murmurs. Valvular heart disease is generally more common in older animals. This is particularly true of aortic valve disease leading to aortic regurgitation. The age of the animal may also affect its use and future use, which may in turn affect the relative significance of cardiac disease. This is usually the most significant consideration.