NBME 21 Arrhythmia (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 3/Question#11 (reveal difficulty score)
A 50-year-old man is found dead in bed at ...
Arrhythmia 🔍 / 📺 / 🌳 / 📖
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+14 upvote downvote
submitted by ∗cantaloupe5(87)

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Histology showed coagulative necrosis (preserved architecture of myocardial fibers) with neutrophil infiltration which hinted that the MI was within 24 hours. Most likely cause of death within first 24 hours of MI is arrhythmia. Myocardial rupture would also be visible on gross appearance of the heart, which they described in the stem.

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bighead478 in FA it shows softening of the myocardium to happen at 3-14 days. Do you think this was overly misleading people (like me) into choosing myocardial rupture? I understand the histo features are consistent with < 24 hours, but the stem should also match this in every detail +16

sbryant6 Myocardial rupture would not happen until 3-14 days. Since this shows signs of <24 hrs, the answer is arrythmia. +3

hello @bighead478 You have to look at the whole picture. Histo shows preserved architecture, which indicates coagulative necrosis -- coagulative necrosis is a histo finding only in the first 24h. The most common causes of MI-related sudden death are: arrythmia > cardiogenic shock (heart pump problem) > rupture. +

jcmed I chose the rupture as well due to the timeline. Somebody gave me this advice the other day, NBME classically will give you an entire vignette leading you somewhere, and the what it asks will be something completely different; or in this case will give you a photo of something and will ask about the photo. They do what they want. +5

athenathefirst Anyone knows why it's not a cardiogenic shock if it was within 24 hours? +5

zevvyt It says "Mottling" which happens in the first day. If it was 3-14 days it would be yellow (p 302 2019). He can be having angina for 3 weeks leading up to an MI. +2

amy The stem of the question said "softening" which indicates 3-14 days (rupture ), and "mottling" which indicate 24h (arrthymia). It seems from the picture in FA2020 page 305, coagulative necrosis would be there during both phases. The cells in the picture are so small that it is hard to tell if it is purely neutrophil or if there are any macrophages. Still seems like a very confusing stem to me. +

+12 upvote downvote
submitted by ∗hungrybox(1277)

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/u/cantaloupe5 had a great explanation.

Here's an image of the different stages following myocardial infarction. Note the "contraction bands" are what define coagulative necrosis.

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+2 upvote downvote
submitted by ∗zpatel(36)

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https://webpath.med.utah.edu/CVHTML/CV127.html

check this out

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smpate Nice find, thanks! +

+1 upvote downvote
submitted by volcanobuns(1)

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MI sudden death -> arrhythmia. The order of commonness is arrhythmia > cardiogenic shock > rupture.

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+0 upvote downvote
submitted by frimmy_11(2)

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Mottling and softening of anterior wall on autopsy suggests it was not older than 24 hrs. Death from fatal arrhythmia like V-fib most commonly occurs within one day of the MI. That said, once scar has formed in myocardial tissue it, too, can cause arrhythmia.

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athenathefirst Anyone knows why it's. not cardiogenic shock since it happened within <24 hours? +

lovebug @athenathefirst I also had same Question. maybe Question asks "Most likely mechanism of death" > most common cause of death in 24hr is arrythmia. cardiogenic shock is also possible. but it's not the most common cause of death within 24hr. +

-1 upvote downvote
submitted by ∗an_improved_me(91)

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Question: even if this pt did have myocardial rupture... is that even a cause of death? I feel like like the mechanism of death in myocardial rupture is cardiogenic shock; blow a hole in your heart, and suddenly it aint pumping so well. Just asking for future reference.

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