USMLE Rx bad question?

[spartan564]

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A 65-year-old man presents to a cardiologist with increasing shortness of breath. He has not seen a doctor in 10 years. He reports that his shortness of breath has been present for several years, but is worsening. He can walk only about 100 feet before becoming short of breath, and he sleeps on four pillows at night. His heart rate is 80/min, blood pressure is 160/100 mm Hg, and respiratory rate is 16/min. Physical examination reveals jugular venous distention, hepatomegaly, and bilateral lower-extremity edema. Laboratory studies indicate negative troponin levels but an elevated B-type natriuretic peptide. An S3 is heard on cardiac examination.
Which infectious agent is most likely responsible for this disease?

There answer is coxsackie virus which is a possibility but they also listed Group A strep as an answer choice which I picked. First aid says that GAS can cause rheumatic fever and thus mitral regurgitation which can you an S3 as well as the dyspnea. Is my reasoning wrong?

 

[Ionian]

Myocarditis is the most common cause of death in the acute phase of rheumatic fever.
Myocarditis is the the number 1 known cause of dilated cardiomyopathy..
I believe if it was through this pathway though you'd expect --> Acute dilation, mitral valve incompetence, death

And he has signs of long standing congestive heart failure.

 

[spartan564]

I was thinking rheumatic heart not acute rheumatic fever (should have made that clear) which causes mitral regurgitation later on in life

 

[Ionian]

I was thinking rheumatic heart not acute rheumatic fever (should have made that clear) which causes mitral regurgitation later on in life

I believe acute is mitral regurg, chronic mitral stenosis

I think if you're going to put down group A step for the answer to dilated cardiomyopathy, it should = acute rheumatic fever which hes not presenting with, and acute rheumatic fever may cause dilated cardiomyopathy, but doesn't present as long standing congestive heart failure (as he is presenting).

You should just be thinking dilated cardiomyopathy/CHF here (the additional symptoms edema, etc.). And I know first aid lists cox in that entry.

 

[boaz]

S3 is associated with dilatation of the LV. Acutely, GAS can cause MR and myocarditis. Those are associated with a regurgitation murmur and (usually) mild troponin elevation, neither of which this patient has. Also, there is nothing in his history to suggest other symptoms of rheumatic fever. Chronically it can cause mitral stenosis, which doesn't cause LV dilatation and is thus not associated with an S3. Coxackie can cause dilated CM, which can present clinically similarly to systolic HF.

 

[shigella123]

I believe acute is mitral regurg, chronic mitral stenosis

I think if you're going to put down group A step for the answer to dilated cardiomyopathy, it should = acute rheumatic fever which hes not presenting with, and acute rheumatic fever may cause dilated cardiomyopathy, but doesn't present as long standing congestive heart failure (as he is presenting).

You should just be thinking dilated cardiomyopathy/CHF here (the additional symptoms edema, etc.). And I know first aid lists cox in that entry.

So, let me see if I understand this right:

Acute RF= no long standing HTN+Myocarditis=dilated cardio-MV incompetence(MR?)= death----- by GAS-pyogenes
vs
Chr RF=Long standing HTN by COX

This pt has dilated cardio+"He reports that his shortness of breath has been present for several years"
= so long standing htn= by COX

 

[Ionian]

yes, I've seen it under these terms "mitral valve incompetence"

idk if its really like MR or MVP since the rapid stretching of the chamber doesn't allow the cusps to even touch one another.

I think you meant to say chronic RF; Mitral stenosis

 

[Wavy Doctor]

I just did a Q in Rx which claimed Coxsackie virus is the most common cause of myocarditis, although Goljan RR says it in fact is adenoviruses. This study is a bit old but seems to back him up: http://www.ncbi.nlm.nih.gov/pubmed/12906974

 

[seminoma]

I just did a Q in Rx which claimed Coxsackie virus is the most common cause of myocarditis, although Goljan RR says it in fact is adenoviruses. This study is a bit old but seems to back him up: http://www.ncbi.nlm.nih.gov/pubmed/12906974

Robbins says coxsackie. Uptodate says coxsackie in children. Can't really use a 2003 study to determine the MCC of something in 2015.