NBME 21 Dissecting aneurysm (NBME Answers)

NBME 21 Answers

nbme21/Block 1/Question#25 (reveal difficulty score)
A 28-year-old man is brought to the emergency ...
Dissecting aneurysm 🔍 / 📺 / 🌳 / 📖
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+7 upvote downvote
submitted by ∗neonem(629)

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Major risk factor for aortic dissection is hypertension, and in this case might be due to cocaine use, which causes marked hypertension. Dissections cause a tear in the tunica intima -- blood can flow backwards into the pericardium and cause tamponade. This manifests as crackles in the lung due to poor left ventricular function (filling/diastolic problem due to compression).

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forerofore there is another clue, the man has diminished pulses in just one arm, which means that the left subclavian artery must be involved somehow, and an aortic dissection would be the best answer explaining this. +11

temmy please why is there where a diastolic mumur? +1

whoissaad @temmy Aortic dissection especially near the root of aorta can lead to dilatation of the aortic valves, which can lead to Aortic regurgitation (diastoic murmur at left sternal border) +9

garibay92 Does anyone know why is this patient's tepmerature elevated? +1

ratadecalle @garibay92, not important for this question I think but cocaine can cause malignant hyperthermia +2

almondbreeze judging by his heart murmur, he probably has marfan syndrome. that's the only place where FA talks about dissecting aneurysm +

almondbreeze he's only 28 - another clue for marfan? +

turtlepenlight did anyone else think it was weird his only sx was SOB? I always think of radiating pain as being a good clue for dissection +3

cmun777 @almondbreeze his heart murmur is at the LSB (aortic regurg) and not consistent with MVP plus no other sx/indication of Marfan. I think the only association of RF you should think about in this question is the cocaine use and consequent HTN. +1

ibestalkinyo @turtlepenlight I agree. I chose another answer because I was like, there's no way this guy doesn't hurt if he's got a dissection. +1

abk93 @whoissaad but aortic regurgitation is a systolic murmur. +

calvin_and_hobbes My guess is that the diastolic murmur is tricuspid stenosis as the tricuspid valve is the most common valve affected in patients who have IVDU +

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submitted by ∗adong(144)

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unequal BP/pulses in the arms is a big key for aortic dissection

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+0 upvote downvote
submitted by ∗readit(18)

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Why is is not pseudo aneurysm?

"Aortic pseudoaneurysms typically occur as a result of trauma +/- intervention, a considered subset of traumatic aortic injury in the majority of cases. They can be acute or chronic."

https://radiopaedia.org/articles/aortic-pseudoaneurysm?lang=us

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readit *same goes for saccular aneurysm, which also is usually 2/2 trauma +

samsam3711 In the question stem there is no indication of trauma so it would be hard to just assume that +

almondbreeze see my comment above for marfan syndrome. might help +

drzed This is because a pseudoaneurysm is between the media and adventitia, and is incited by trauma; a dissection is between the intima and the media and is a result of hypertension causing an intimal tear. The history points toward cocaine -> hypertension rather than penetrating trauma. +

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submitted by ∗meryen13(48)

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just remember that cocaine is one of the common causes of aortic dissection in young people. there are other causes that are genetic such as marfan, but in this question its clearly mentions cocaine abuse. the pain of dissection radiates to the back and its sharp. widened mediastinum is also a key.

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