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Retired NBME 15 Answers

nbme15/Block 1/Question#27 (reveal difficulty score)
A 50-year-old man comes to the physician ...
Stenosis of the right coronary artery ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–
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submitted by โˆ—cassdawg(1781)
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Key aspects of the question:

  • Hypokinesis of the posterior left ventricle with increasing activity levels - in my opinion this is the primary clue to stenosis of the right coronary artery. This is because the posterior heart is supplied by the posterior descending artery, which in most people who have right dominant coronary circulation is a branch of the right coronary artery.
  • "When climbing stairs" and the hypokinesis being present on stress testing - this helps you to know the condition is only exacerbated in exercise, and stenosis of the RCA generates symptoms in exercise because in excersise the increase in oxygen demand typically causes dilation of the coronary vessels to accomadate. When there is stenosis, the vessel cannot dilate and thus there is transient ischemia of the area the vessel supplies (this is potentially exacerbated by the coronary steal phenomenon in a stress test which can occur with administration of vasodilators) FA2020 p304

Increase in oxygen consumption is the normal response to exercise and alone is not pathologic. Extravascular compression of the coronary arteries is also considered normal and nonpathologic; this is why most coronary blood flow occurs during diastole and why the endocardium is most susceptible to ischemia.

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euchromatin69  but isnt stenosis gonna cause m.infarction? we have not been told any percentage of stenosis +
shieldmaiden  If it completely cuts off blood for too long, then yes, but as you mentioned, they don't tell us how much stenosis, so with his clinical presentation and echo, we can say it's stable angina. Like @cassdawg mentioned, here a case of transient ischemia +



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