NBME 24 Fixed cardiac output in spite of increased demand (NBME Answers)

NBME 24 Answers ↦

nbme24/Block 4/Question#11 (reveal difficulty score)
A 53-year-old woman comes to the physician ...
Fixed cardiac output in spite of increased demand🔍,📺
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+20
submitted by marbledoc(0),

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taWh is hits mentoacdii ngibe sddercbei e?hre naC mesneoo mehic .in

+11
submitted by ∗neonem(590),

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iths tntepai ash mctipoyasmt iartoc noies.sst isTh cna be itfeeididn by hte catrivruenl ppeyrotrhhy (to atmsecnpeo for ceinrsaed ftnluacion doraeaflt rfmo cpmio-nannlto iorcta e,)lvav cmstslyidoi urmmur adn teh lnotoiac at eth molarn rcoiat a.ear

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guillo12 What does "fixed cardiac output" signify? +1

usmleuser007 "fixed cardiac output" might mean that with the stenosis (ie. narrowed aortic valve) there is a limited or rather reduced cardiac output. Exercise would not increase cardiac output because the stenosis is caused by a mechanical (physical) rather than a biochemical process. Therefore, At any given moment the heart can not increase its output no matter how forcefully it contracts. +10

fallot4logy why not option A?arterial compression ? +3

sunshinesweetheart @fallot4logy LVH does not lead to coronary artery compression. only reallyyyy rarely will pulmonary artery dilation cause coronary artery compression. plus that would cause angina but probably wouldnt decrease cerebral bloodflow to syncope. her murmur + LVH point us toward aortic stenosis which does cause those --> fixed CO +2

drpatinoire @fallot4logy LVH can cause coronary artery compression, but typically leading to coronary ischemia after exercise (i.e. stable angina in this patient). The question is asking what leads to her syncope. Syncope actually means her brain is lacking blood supply abruptly. +5

rainlad how do we rule out mitral valve prolapse in this case? +

spow @rainlad murmurs at the right upper sternal border are aortic in nature. Mitral murmurs are heard at left 5th intercostal at the midaxillary line. +1

jj375 Also, nobody mentioned the "prominent left ventricular impulse". I kinda get thrown off by these. Anyone have thoughts? Google was telling me it is from a hypertrophied ventricle so I'm thinking her aortic stenosis causes the LV hypertrophy and an impulse. Is this the correct line of thinking? +

+8
submitted by ∗usmile1(129),

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cbreland Great, same thought process, murmur made me think of aortic stenosis, supported by the LV hypertrophy in stem. Then you have syncope during exercise because the heart is not able to keep up with the demands of the body +

+0
submitted by ∗aneurysmclip(178),

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