Patent ductus arteriosus

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Patent ductus arteriosus

Cardiovascular system

Cardiac tumors

Cardiac tumors




Patent ductus arteriosus


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Patent ductus arteriosus

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USMLE® Step 1 style questions USMLE

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A 25-year-old man is referred to a cardiologist for evaluation for intermittent cyanosis and exercise intolerance. Symptoms began around half-a-year ago, and they have progressively worsened. Past medical history is notable for a congenital heart defect, which was diagnosed shortly after birth. However, he was subsequently lost to follow-up and was not treated for this condition. The patient smokes half-a-pack of cigarettes per day. Physical exam is notable for cyanosis of the lips and clubbing of the fingers. Cardiac catheterization is performed, and oxygen saturation in the cardiac chambers and outflow tracts are shown below:  

 Which of the following is the most likely explanation of these findings? 

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patent ductus arteriosus p. 305

Heart murmurs p. 298

patent ductus arteriosus p. 305

Patent ductus arteriosus (PDA)

congenital rubella p. 306

fetal alcohol syndrome p. 306

heart murmur with p. 298

indomethacin for p. 499

mechanism and treatment p. 305

misoprostol for p. 408

neonatal respiratory distress syndrome and p. 685


Patent — not in the sense of a patent for an invention — refers to some opening. A patent ductus arteriosus, or PDA for short, refers to a blood vessel, the ductus arteriosus, which connects the pulmonary artery to the aorta during fetal development. The ductus arteriosus is right on the aortic arch where vessels branch off to the brain and upper extremities. All right, so to help visualize this, let’s look at a super simplified version of the heart to show the relationship between the aorta, branches, pulmonary artery, and ductus arteriosus. We’ll still keep the more anatomical heart for reference. So, the ductus arteriosus usually closes after birth because the walls collapse down; this vessel becomes a ligament, the ligamentum arteriosum. When it stays open after birth, we call it a patent ductus arteriosus because it’s still passing blood through it; in other words, it’s still patent.

Now, during development, the fetus doesn’t use the lungs yet; instead, it relies on oxygenated blood from the placenta, which comes into the right atrium. Most of that blood actually flows through the foramen ovale, an opening between the atria. Blood that doesn’t make it through the foramen ovale is pumped out of the right ventricle into the pulmonary artery, at which point most of it gets sent through the ductus arteriosus to the aorta instead of to the lungs. Remember, the fetus isn’t using the lungs yet.

During fetal development, the ductus arteriosus is kept open by high levels of a vasodilator prostaglandin E2, which is made by the placenta and the ductus arteriosus. At birth, a bunch of things change. First, oxygen levels in the blood go up dramatically and the lungs become the main source of oxygenated blood. Soon after birth, the foramen ovale closes and prostaglandin E2 levels fall, causing the ductus arteriosus to close off. The lungs also start to release a small peptide called bradykinin, which constricts the smooth muscle wall of the ductus arteriosus and sort of helps the process along. Within the first day, the ductus arteriosus usually starts clamping shut; within three weeks, it’s completely closed off and turned into the ligamentum arteriosum. If the ductus arteriosus doesn’t close, then the baby is left with a patent ductus arteriosus. This condition accounts for about 10% of all congenital heart defects, of which the vast majority, about 90%, are isolated heart defects, meaning there aren’t any additional congenital defects. On the other hand, a PDA can be associated with other congenital problems, such as congenital rubella syndrome, which happens when the mother contracts rubella virus during her pregnancy.


Patent ductus arteriosus (PDA) is a congenital heart defect in which the ductus arteriosus, a blood vessel that normally closes after birth, remains open. During fetal development, the ductus arteriosus connects and shunts blood from the pulmonary artery to the aorta, because the fetus doesn't use its lungs yet.

Initially, PDA causes a left-to-right shunt, resulting in pulmonary hypertension. Over time, as the pulmonary artery pressure increases, this is converted into a right-to-left shunt. This switch in the shunt is known as Eisenmenger's syndrome. PDA can be treated with the drug indomethacin, or by surgical ligation.


  1. "Clinical manifestations and diagnosis of patent ductus arteriosus in term infants, children, and adults" undefined (2015)
  2. "Rapid Review Pathology (4 edition)" Elsevier (2013)
  3. "Patent ductus arteriosus (PDA) clinical presentation" undefined (2016)
  4. "Robbins Basic Pathology (10 edition)" Elsevier (2017)
  5. "Patent ductus arteriosus" undefined (undefined)
  6. "Fundamentals of Pathology: Medical Course and Step 1 Review" Pathoma (2017)

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