Atrial Septal Defect
Atrial septal defect is the condition where there is persistence of the communication - the foramen ovale - between the two atria which is necessary in the foetus to allow oxygenated blood from the placenta, which enters the right side of the heart, to cross to the left and then round the circulation. When the baby, at birth, takes its first breaths and the cord is clamped, the pressure on the left side of the heart increases, while that on the right drops. The foramen ovale is closed by a flap of tissue arising from the wall of the left atrium. When this fails, there is flow of blood from the left atrium to the right - a left-to-right shunt. This is one of the conditions known as a ‘hole in the heart’. Since the movement of blood is from the left (full of oxygen having been round the lungs) to the right, it does not cause the baby to appear blue, and it does not necessarily adversely affect the health of the child. It can, however, be a cause of endocarditis, so antibiotics should be given before surgical procedures, and since it exposes the right side of the heart to increased pressure it can lead to right sided heart failure. In some children it causes recurrent chest infection and wheeze, and in older people disturbances of heart rate and rhythm. In order to prevent these problems most children are offered surgery to correct the defect.
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