Describe the Patent Ductus Arteriosus?

It is the persistence of normal fetal channel connecting the aorta and pulmonary artery. It accounts for 5-10 per cent of all CHDs. Functional closure of the ductus occurs within 12-24 hours after birth due contraction of the medial smooth muscle. Anatomic closure occurs between 2-3 weeks and is produced by fibrosis of the ductal tissue. In cases where the ductus fails to close normally, blood will shunt from left to light into PA and lungs. This occurs increasingly as the PVR drops and the pressure in the aorta exceeds that of PA. The volume of shunted blood will increase pulmonary blood flow, increase venous return to LA and cause LA /LV volume overload. The flow in the PDA occurs throughout the cardiac cycle. This results in a murmur which starts in systole after S1, peaks at S2 and continues in diastole. This is continuous murmur. The passage of increased blood across the mitral valve produces MDM. The prolonged LV systole results in delayed closure of the aortic valve and a late A2.With large L>R shunts the S2 may be paradoxically split.

Figure: Patent ductus arteriosus