Abstract
The ductus arteriosus is a vessel which is essential for the fetal circulation but which ceases to be necessary after birth when expansion of the lungs allows more blood to flow through the enlarged pulmonary vascular bed. Having fulfilled its function in prenatal life the ductus normally becomes closed off following delivery of the child. Christie1found that 95 per cent of routine postmortem subjects at 12 weeks of age had a closed ductus and that 98.8 per cent of them at 1 year had this vessel obliterated. If the ductus arteriosus remains open during childhood or later life, the passage of blood through it (from the aorta to the pulmonary artery) forms an arterial leak which may assume considerable importance. If the ductus is small, the patient can indulge in reasonable activity and may have a normal life expectancy. If, however, the ductus is relatively large, physical work