NBME Step 2 CK Form 8 Closure of the ductus arteriosus (NBME Answers)

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NBME Step 2 CK Form 8 Answers

step2ck_form8/Block 2/Question#38 (reveal difficulty score)
A 3-day-old newborn is brought to the ...
Closure of the ductus arteriosus 🔍 / 📺 / 🌳 / 📖
tags: cardio inc

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submitted by ∗step_prep(148)

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This is a classic presentation for a patient with coarctation of the aorta. When they are first born, blood is able to get past the coarctation because blood flow through the ductus arteriosus enters the aorta distal to the coarctation. When the ductus arteriosus closes in the first week of life, the left side of the heart then sees a massive increase in afterload, leading to heart failure

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azibird Is the patent foramen ovale required for this? Apparently it stays open for 6 months to a year. Because otherwise I can't understand how the PDA distal to the coarctation would be helpful. So does PFO then PDA help divert LA blood into the descending aorta? According to UTD: "During the neonatal period, when the PDA and foramen ovale (between the right and left atria) begin to close, the cardiac output that must cross the narrowed aortic segment to reach the lower extremities steadily increases." +

jj375 @azibird sometimes the PDA is proximal to the coarctation! https://assets.aboutkidshealth.ca/AKHAssets/Hearts_CHD/Coarctation.jpg?RenditionID=19 +

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submitted by ∗spiroskeet(31)

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This was a poorly worded question – the underlying mechanism of the child's condition is narrowing of the aorta, causing backup into the heart and upper body. If they wanted to get at why it presented after 3 days instead of immediately, maybe just maybe they should've asked that instead.

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notyasupreme Agreed! This is worded so badly, and is so classic NBME! I guess it couldn't have been the others because increase in peripheral vascular resistance isn't technically counted as the aorta. +

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