USMLE - Libman-Sacks endocarditis

[Phloston]

Any cardio experts out there?

So far I've come across two questions in QBank on Libman-Sacks endocarditis.

The first one gave a vignette of a pt who clearly had SLE, then asked about the heart pathology (no additional information was given relating to heart sounds or CXRs, etc.). I limited the answers down to aortic regurgitation and mitral stenosis, and mitral STENOSIS was correct. That being said, I was shocked because we always hear that 99% of MSs are rheumatic fever-induced.

Moving along..

The second question came down to a left-sided systolic murmur. Keeping in mind that I had encountered mitral stenosis with the previous question and that MSs rarely occur from anything other than rheumatic fever, I figured there MUST be a proclivity for the Libman-Sacks-induced verrucae (on both sides of the valve) to cause STENOSIS. The answer choices were mitral regurgitation and aortic stenosis, so I went with the aortic stenosis, particularly because I've read on PubMed that LS endocarditis can occur on the mitral AND/OR aortic valves. Anyway, the answer was mitral regurgitation.

I am left with the impression that USMLE Step1 is focused on specifically mitral valve involvement in LS endocarditis, versus aortic pathology, irrespective of whether the particular valvular changes demonstrate incompetence versus stenosis.

This concerns me because although LS endocarditis may be "classically" mitral (with regurgitation that could potentially progress to stenosis), I would still think that MR > AR > AS > MS.

Does anyone have any thoughts about this stuff?

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[futuredoctor10]

That's interesting the QBank emphasized this so much (was it UWorld?)

My understanding is that the valvular lesions of LSE are usually asymptomatic, but occasionally cause mitral regurgitation. That's interesting PubMed discusses aortic valve involvement as a possibility but I think we learned "classically" its mitral regurgitation.

 

[Phloston]

was it UWorld?

I'm referring to USMLE Rx QBank.

 

[Bernoull]

Any cardio experts out there?

So far I've come across two questions in QBank on Libman-Sacks endocarditis.

The first one gave a vignette of a pt who clearly had SLE, then asked about the heart pathology (no additional information was given relating to heart sounds or CXRs, etc.). I limited the answers down to aortic regurgitation and mitral stenosis, and mitral STENOSIS was correct. That being said, I was shocked because we always hear that 99% of MSs are rheumatic fever-induced.

I'm not sure what other answer choices u had, but libman-sachs tends to involve the MV causing regurg. It can also affect the AV (actually it can affect ALL 4 valves) but the most likely involvement = MV. now, it can cause BOTH regurg & stenosis, but stenosis is much rarer. The best answer would have been MV regurg IF it was offered, but b/t AV regurg & MV stenosis, the latter is more likely. Goljan RR doesn't even mention AV involvement, it's just not very common.

U're absolutely right most MS are caused by RF, but given no Hx of RF (I'm assuming here) AND given Hx of SLE, they want libman-sachs NOT RF/MS, the vignette can change everything and rare Dzs are extremely common on board exams.. go figure

RR Path & Pathoma
http://emedicine.medscape.com/article/155230-overview#a0104
http://emedicine.medscape.com/article/155230-overview#a0101

Moving along..

The second question came down to a left-sided systolic murmur. Keeping in mind that I had encountered mitral stenosis with the previous question and that MSs rarely occur from anything other than rheumatic fever, I figured there MUST be a proclivity for the Libman-Sacks-induced verrucae (on both sides of the valve) to cause STENOSIS. The answer choices were mitral regurgitation and aortic stenosis, so I went with the aortic stenosis, particularly because I've read on PubMed that LS endocarditis can occur on the mitral AND/OR aortic valves. Anyway, the answer was mitral regurgitation.


See explainer above... MV regurg >>>>>>>>>> MV sten > AV anything for Libman-Sachs, it's all about probability here, everything is possible but somethings are more probable.. Also I'm not sure if the heart murmur was described, but this would be another way of ruling out stenosis over regurg

This is how I think of why regurg > stenosis: LSE = buildup of gunk on leaflets, I shouldn't take much gunk buildup to WEIGH DOWN the leaflet such that the commissures don't line up perfectly upon closure = insuff./regurg. Now think about how much gunk has to build up to meaningful (>50%) narrow the aperture and cause stenosis.

For a more rigorous explanation, consider fluid dynamics and (specifically) Gorlin's Eq and it's application/implication in stenosis. Gorlin's Eq can be modeled as cross-sectional valve area ~ (flow/pressure gradient) AND >50% stenosis is required to meaningful reduce flow across ANY valve... Now think about how much gunk has to build up to block >50% of the valve aperture....


I am left with the impression that USMLE Step1 is focused on specifically mitral valve involvement in LS endocarditis, versus aortic pathology, irrespective of whether the particular valvular changes demonstrate incompetence versus stenosis.

Ur suspicion is right right that LSE affects MV >>>AV & regurg>>stenosis.

This concerns me because although LS endocarditis may be "classically" mitral (with regurgitation that could potentially progress to stenosis), I would still think that MR > AR > AS > MS.

I think it's MR>MS>AR>AS...

Does anyone have any thoughts about this stuff?

I'll bite....

Also from Robbins:
Endocarditis of Systemic Lupus Erythematosus (Libman-Sacks Disease):
"...Thrombotic heart valve lesions with sterile vegetations or rarely fibrous thickening commonly occur with the antiphospholipid syndrome ... The mitral valve is more frequently involved than the aortic valve; regurgitation is the usual functional abnormality..."

 

[Phloston]

Thank you for the comprehensive reply, Bernoull. Helpful to hear your thoughts.

 

[Bernoull]

Thank you for the comprehensive reply, Bernoull. Helpful to hear your thoughts.

U're welcome. Sorry for the typos, hopefully it didn't distract too much from what I was trying to say... these r the perils of posting at 3am