NBME 22 Insertion of transvenous pacemaker (NBME Answers)

Retired NBME 22 Answers

nbme22/Block 2/Question#29 (reveal difficulty score)
A 79-year-old man is brought to the emergency ...
Insertion of transvenous pacemaker 🔍 / 📺 / 🌳 / 📖
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+4 upvote downvote
submitted by ∗mattnatomy(46)

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A Pacemaker is the correct treatment for 3rd degree AV block. Makes it so the atria and ventricles beat in sync.

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leaf_house Why wouldn't you do a transesophageal echo, just to establish what you're dealing with? +

greentea733 I think since you already did an ECG and you know it's for sure 3rd degree AV block, TEE probably wouldn't change the management at all, so you wouldn't want to expose pt to extra risk of a procedure (however minor it may be). I feel like more invasive testing typically is not the correct answer when you can avoid it, as a general theme. +5

orthonerd @leaf_house - Whenever two imaging tests that are similar with advanced clinical decision making tools being used to decide which one to do (TEE vs TTE)- I generally assume that I can eliminate both as a choice- especially in this case where the definitive Tx is a choice. +2

+1 upvote downvote
submitted by ∗usmleboy(19)

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Could someone explain why "Cardiac catheterization with stent placement" is incorrect?

My thought process was that this guy has an occlusion of his RCA --> knocking out his AV node --> 3rd degree AV block. Also his pulse is 40 which suggest a RCA infarction as well.

The reason I went with this is because he got to the hospital within 30 minutes and they put this information first and made it seem important. If his RCA could be opened up, then the damage could be reversible.

I get the pacemaker, but first I feel like you would attempt to unocclude the vessel and give it some integrity.

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hajdusa That choice is incorrect because you can't assume that he has an occlusion from the information that you have. There can be many etiologies of a heart block, and they do not have to be ischemic in nature - for example there are different microbes that can cause heart block too. Additionally, if this guy were to have an RCA occlusion you'd likely see evidence of ischemia or infarction on the ECG but the only findings we're given are bradycardia and 3rd degree block. Hope this helps! +2

mtkilimanjaro Also, the two cardiac catherization options would ultimately result in a similar outcome. It's like how the poster above mentioned the two imaging are very similar that you can rule them out. +

an1 AV block treatment is with a pacemaker. Straight from FA. The only time you'd want to do stenting is when there is stenosis (>70%) leading to angina, or an MI. Those could be potential differentials here but they flat out said he had an AV block so it's not the best approach. Also, the RCA supplies the SA node, the PDA supplies the AV node. AV block is due to AV node, Sick sinus syndrome would be due to SA node (dropped P wave rather than QRS. +1

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submitted by ∗doso2222(12)

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First 2 heart blocks --> NO TREATMENT (1st degree and 2nd degree Mobitz type I)

Last 2 heart blocks --> PACEMAKER (2nd degree Mobitz type II and 3rd degree)

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