Since you are now "experts" on the large blood vessels - the aorta and pulmonary artery - its easy to learn about the birth defect called Patent Ductus Arteriosus (or PDA)..

What is a PATENT DUCTUS ARTERIOSUS ?

As a child develops inside its mother's womb, it is not able to "breathe". So, even though the child's lungs are well developed, they do not carry out their normal work. The blood which flows through the right ventricle and pulmonary artery to the lungs has no function. It is "wasted" blood flow.
In an attempt to make use of this flow, nature provides man with a "shunt" or "bypass". A small tube, or blood vessel, connects the pulmonary artery to the large artery called the aorta. This tube is the DUCTUS ARTERIOSUS.
Through this tube, blood which enters the pulmonary artery, instead of going to the lungs, flows into the aorta. From the aorta, the blood reaches other parts of the body. It is now useful to these other parts, which get energy to do their work.
At birth, when the child draws its first breath, the lungs begin to work. Now, when blood flows into the lungs, it is mixed with oxygen and "purified". At this time, the ductus arteriosus normally closes. At first, it closes by spasm or contraction of the muscle in its wall. Later, the tube becomes permanently blocked by a scar. Sometimes, it DOES NOT CLOSE normally. It then remains open, and the condition is called PATENT DUCTUS ARTERIOSUS - or PDA.

What happens in a PDA ?

I have told you about the changes that happen in an atrial or ventricular septal defect (ASD and VSD). A PDA is somewhat similar. In a PDA too, more blood flows into the lungs than normal. The blood flow in the PDA is from the aorta to the pulmonary artery, and then to the lungs. This is in the opposite direction to flow that occurs before birth. The reason is that, soon after birth, the pressure in the aorta becomes very high. So blood, like any fluid, flows from a high pressure area (aorta) to a lower pressure area (pulmonary artery).
The extra blood in the lungs, like in ASD and VSD, causes frequent "chest colds". It also increases the lung blood pressure, and over the years makes the blood vessels and thick - PULMONARY HYPERTENSION. When the PDA is large, and particularly in small children, the enormous blood flow may cause HEART FAILURE. The small ventricle is not able to pump out all the blood entering it, and "fails". The child has fast shallow breathing, excessive sweating, inability to feed well, irritability, constant crying, and a failure to grow normally. Early repair may be needed in these cases.
An interesting fact about PDA is that, like in a VSD, when you place your palm over the patient's chest, you feel a soft thrill, like a kitten purring! The reason for this is the forceful and turbulent blood flow across the PDA.

What happens if PDA is left untreated ? Find out .....

 

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