Patent Ductus Arteriosus | Symptoms and Causes

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What is patent ductus arteriosus?

All babies are born with a small opening between their pulmonary and aortic valves.

  • While a baby develops in the uterus, it’s not necessary for blood to circulate through his lungs because oxygen is provided through the placenta.
  • During pregnancy, this opening is necessary to allow oxygen-rich (red) blood to bypass the baby's lungs and flow into the body.
  • This passageway is called a ductus arteriosus.

At birth, when the placenta is removed, the baby's lungs must now provide oxygen to his/her body. As the baby takes the first breath, the blood vessels in the lungs open, and blood begins to flow through and pick up oxygen.

At this point, the ductus arteriosus is not needed to bypass the lungs. Under normal circumstances, within the first few days or weeks after birth, the ductus arteriosus closes and blood no longer passes through it. Most babies have a closed ductus arteriosus within 72 hours of being born.

In some babies, however, the ductus arteriosus remains open (patent). The opening between the aorta and the pulmonary artery allows oxygen-rich (red) blood to pass back through the blood vessels in the lungs. This is called patent ductus arteriosus.

How common is patent ductus arteriosis?

Patent ductus arteriosis is the sixth most common congenital heart defect, occurring in 5 to 10 percent of all children born with congenital heart disease. Patent ductus arteriosus occurs twice as often in girls as in boys.

What causes patent ductus arteriosus? 

Almost all children have a PDA present at birth. In some children, the PDA does not close, and remains open and the condition now becomes knows as patent ductus arteriosus (PDA). Although exact reasons why this happens in some patients and not in others are not knows, the most common association for a PDA is prematurity.

PDA also can occur in combination with other heart defects.

Why is patent ductus arteriosis a concern? 

When the ductus arteriosus stays open, oxygen-rich (red) blood passes from the aorta to the pulmonary artery, mixing with the oxygen-poor (blue) blood already flowing to the lungs. The blood vessels in the lungs have to handle a larger amount of blood than normal. How well the lung vessels are able to adapt to the extra blood flow depends on how big the PDA is and how much blood from the aorta is able to pass through it.

Extra blood causes higher pressure in the blood vessels in the lungs, a condition called pulmonary hypertension. The larger the volume of blood that goes to the lungs, the higher the pressure.

The lungs are able to cope with this extra blood flow and pressure for a while, depending on exactly how high the pressure is. Without medical treatment, however, the blood vessels in the lungs become diseased by the extra pressure.

Also, because blood is pumped at high pressure through the PDA, the lining of the pulmonary artery becomes irritated and inflamed. Bacteria in the bloodstream can easily infect this injured area, causing a serious illness known as bacterial endocarditis.

What are the symptoms of a patent ductus arteriosus? 

The size of the opening between the aorta and the pulmonary artery will affect the type of symptoms, the severity of symptoms and the age at which they first occur. The larger the opening, the greater the amount of blood that passes through and overloads the lungs. 

A child with a small patent ductus arteriosus might not have any symptoms, and your child's physician may only have discovered the defect by hearing a heart murmur. Infants with a larger PDA may exhibit different symptoms. The following are the most common symptoms of PDA: 

  • fatigue
  • sweating
  • rapid breathing
  • heavy breathing
  • congested breathing
  • disinterest in feeding, or tiring while feeding
  • poor weight gain

The symptoms of PDA may resemble other medical conditions or heart problems. Always consult your child's physician for a diagnosis.

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