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The ductus arteriosus is a structure present in the fetal heart that helps to improve fetal blood circulation. It is a pathway between the aortic and pulmonary arteries that allows blood to mix between these two arteries, which means that blood flows easier. Usually this communication closes within the first few days of life, but if it doesn’t, the condition is called patent ductus arteriosus (PDA). PDA still may resolve without treatment or might require medical or surgical intervention.
Fetal oxygen is obtained through the umbilical cord, instead of by exchanging gases in the lungs. Much of the bloodflow to the lungs that occurs when people breathe is not occurring in the fetus, because the circulatory system bypasses this process. Both the ductus arteriosus and the ductus venosus, a small communication or hole in the two atria, reduce the amount of blood flowing to the lungs by shunting it into the left side of the heart. The mixing of oxygenated and unoxygenated blood doesn’t matter in fetal circulation due to the higher oxygen bearing properties of each blood cell and the dependence on the mother for an oxygen supply.
When a newborn takes a breath, circulatory patterns change dramatically. Suddenly, the lungs are involved and the heart has new demands. The increase of left ventricular pumping and rapid bloodflow makes mixing of the blood undesirable. Blood shunting to the right of the heart from a ductus arteriosus can overwhelm the right side of the heart and raise pressure in the lungs. In most cases, the act of breathing starts to shut the ductus arteriosus; as circulatory patterns change, this communication closes, often by the third day of life outside of the womb.
In some cases, the closure doesn’t occur, and this condition, which can be detected by a faint heart murmur, can require no more than observation. Alternately, persistent PDA may create high lung pressure or cause problems like poor oxygenation to the body. Failure to close is most common in premature infants who are thought to have a 30% rate of PDA. In these instances or in older children or adults with PDA, doctors may use medicine, catheter interventions like spring coil devices, or they can intervene surgically to perform the necessary closure.
In the treatment of more severe newborn heart defects, preventing the closure of the ductus arteriosus may be vital in the first few days of life. Prostaglandins can help keep this communication open for a few more days, when there are other profound defects altering heart function. Some surgeries, like the Blalock-Taussig shunt, replicate the function of the ductus arteriosus until children are slightly older and can have additional repairs to their hearts that more properly restore normal circulation.
Though PDA is one of the most common heart defects, it is still relatively uncommon. It fortunately can be detected by careful listening with a stethoscope. Even if the ductus arteriosus doesn’t close for a few months, this may not be concerning. Poor weight gain or growth, fatigue, blueness at the extremities, or difficulty breathing are indications that more medical intervention is needed. If children have this condition and are otherwise healthy, there is usually no indication to intervene. Should parents feel uncertain about the recommended course, a consultation with a pediatric cardiologist is suggested.
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