Effect of Standing on Aortic Stenosis Murmur - USMLE Forums
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  #1  
Old 01-13-2012
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Stethoscope Effect of Standing on Aortic Stenosis Murmur

Why does standing up increase the murmur from aortic stenosis (sytolic ejection murmur).
Standing up -- descrease RA return, thus decrease SV. I don't understand how a decreased SV means u get a louder murmur. the only thing i can come up with is that in aortic stenosis, by standing up u increase TPR so u make the stenosis worse ?

True ? False ?
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Old 01-14-2012
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what i know standing up decreases aortic stenosis murmur

standing up increases hypertrophic cardiomyopathy murmur

i hope u r not confusing AS with HCM
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Old 01-14-2012
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i double checked
Q id 189[355135] choice B explanation --- standing up increases the SEM of hypertrophic obstructive cardiomyopathy.
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Old 01-14-2012
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hypertrophic obstructive cardiomyopathy and aortic stenosis are not same pathology they r different

standing up decreases aortic stenosis murmur but increases hypertrophic obstructive cardiomyopathy murmur
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Old 01-14-2012
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Standing up causes decrease in Preload, this means less blood going into the superior vena cava, this causes a decrease in the murmer of an already stenosed murmer, where as squatting or reclining which causes an increase in Preload increases this murmer. Opposite is true for HOCM where you want more blood to force out of a hypertrophied interventricular septum so that blood goes out well on increaseing preload....

In Mitral Valve prolapse where there is mid-systolic click, increaseing pre-load by standing up or valsalva manoever or exercise the midsystolic click moves closer to S1 and decreasing preload makes it closer to S2.!!!
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Old 01-14-2012
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Quote:
Originally Posted by step_enhancer View Post
what i know standing up decreases aortic stenosis murmur

standing up increases hypertrophic cardiomyopathy murmur

i hope u r not confusing AS with HCM
how does standing up (decreasing venous return) increase a hypertrohpic cardiomyopathy murmur?
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Old 01-14-2012
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Quote:
Originally Posted by khushi.chahal View Post
how does standing up (decreasing venous return) increase a hypertrohpic cardiomyopathy murmur?
see HCM as a dynamic obstruction due hypertropied interventricular septum.

so standing up ----reduced preload(due to peripheral pooling of blood)-----less blood in left ventricle----obstruction increased due to thick intervenritcular septum .

so ejection murmur increased of hcm due to increased obstruction caused by the
hypertrophied interventricular septum.
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Old 01-14-2012
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Quote:
Originally Posted by step_enhancer View Post
see HCM as a dynamic obstruction due hypertropied interventricular septum.

so standing up ----reduced preload(due to peripheral pooling of blood)-----less blood in left ventricle----obstruction increased due to thick intervenritcular septum .

so ejection murmur increased of hcm due to increased obstruction caused by the
hypertrophied interventricular septum.
ok so its already a diastolic filling dysfunction, and by decreasing the preload, you are furthering the filling dysfunction, right? hence, a worsened condition and murmur?
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Old 01-14-2012
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Quote:
Originally Posted by khushi.chahal View Post
ok so its already a diastolic filling dysfunction, and by decreasing the preload, you are furthering the filling dysfunction, right? hence, a worsened condition and murmur?
diastolic dysfunction is because the ventricle has undergone so much hypertrophy that the lumen volume has significantly reduced also the myofibrils are derranged (lost their normal arrangement due to excessive hypertrophy)

and murmur is due to reason i already mentioned the hypertrophied interventricular septum obsrtucting the outflow tract when the preload has decreased.

the two are due to diff reasons !
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Quote:
Originally Posted by step_enhancer View Post
diastolic dysfunction is because the ventricle has undergone so much hypertrophy that the lumen volume has significantly reduced also the myofibrils are derranged (lost their normal arrangement due to excessive hypertrophy)

and murmur is due to reason i already mentioned the hypertrophied interventricular septum obsrtucting the outflow tract when the preload has decreased.

the two are due to diff reasons !
if the murmur is due to the IV septum obstructing outflow, how does decreased preload worsen that obstruction?
if anything, there is less blood to be pushed through that obstructed exit so the murmur should be less :/
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Old 01-14-2012
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Try to understand... This is because... suppose you have an obstruction, suppose you have a hill that you need to jump?? how will you do it??? you need to push extra effort to pass over that hill, similarly when this blood can only pass through this hill in the heart if it increase its preload and push off the barrier of this interventricular septum!!! IF IT DECREASE THE PRELOAD THIS MUSCULAR OBSTRUCTION WILL NEVER LET IT GO THROUGH IT.... i hope you get my point!!

Last edited by doctorFH; 01-14-2012 at 08:28 AM.
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Quote:
Originally Posted by doctorFH View Post
Try to understand... This is because... suppose you have an obstruction, suppose you have a hill that you need to jump?? how will you do it??? you need to push extra effort to pass over that hill, similarly when this blood can only pass through this hill in the heart if it increase its preload and push off the barrier of this interventricular septum!!! IF IT DECREASE THE PRELOAD THIS MUSCULAR OBSTRUCTION WILL NEVER LET IT GO THROUGH IT.... i hope you get my point!!
yes nice i think it will help

@khushi.payal also see a picture of HCM and refer a book .hope u understand

tc
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Old 01-14-2012
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Ah i was only thinking of preload as a measure of venous return, not as a measure of ventricular stretch and all that. In that sense i suppose it makes sense.

Thanks guys!
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Old 01-14-2012
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I will add up to the above discussion.
In increase preload Lt ventricle is filled so it seperates interventricular septum from lt atrium leaflet(Remember is produced of narrow space between interventricular septum and mitral valve).Hence moving of blood between them produces murmur of low intensity.
In decrease preload they are not seperated and the flow through the space between interventricular septum and mitral valve is narrowed hence increase in murmur intensity.
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Old 02-28-2012
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Default effects of standing

These are the effects of standing, what can lead to syncope, and how body compensates

Standing after 5 minutes or so--> increase venous pressure (blood pooling in veins) leading to increased filtration into lymphatics in lower limb, decreasing the venous volume, decreasing venous return to the heart, decreasing cardiac output, reducing blood volume to the brain and leading to syncope
To compensate:
MAP will sense this reduction and the decreased baroreceptor firing to the nucleus tractus will cause decrease in parasympathetic response and increase in sympathetic response leading to INCREASED heart rate, contractility, and arterial resistance. In addition-->skeletal muscles contract, reduce lympathic filtration, blush is pushed to the thoracic region, increasing central venous return and pressure.

Overall this applies to your questions because in hypertrophic myopathy the murmur will intensify with increased heart rate/ increased demand on the heart, this is why when you stand up you can hear this ejection murmur.
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Cardiovascular-, Clinical-Signs, Physiology-

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