why sudden standing increase murmur of HCM?

[match2011]

my understanding is : sudden standing decrease venous return, decrease LVEDV, then decrease obstruction, murmur decrease too.

Confused from UW: decreased LVEDV enhances obstruction , then increase murmur.

any explanation?

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[harv1212]

it's cause it's a diastolic dysfunction ... therefore anything that reduces filling will exacerbate the diastolic dysfunction ... how a cardiologist explained it to me

 

[username456789]

The idiot's explanation (i.e. mine) is that less EDV means the ventricle is more "collapsed" and allows the obstruction to become more pronounced (I'm extremely tired and unable to summon the correct terminology, but picture all the crap collapsing in on itself and exacerbating the obstruction).

This is like one big thing every school probably stresses in cardiology, so it's worth getting right. The outflow obstruction/murmur of HCM essentially operates opposite that of Aortic Stenosis.

So, for HCM, sudden standing = decreased venous return = decreased LVEDV = INCREASED obstruction = INCREASED murmur.

Edit: I guess it's the anterior MV leaflet or whatever that hits the IV septum. With decreased preload/EDV, you have a greater likelihood it will make contact with the septum.

 

[match2011]

Thanks

 

[1nycdoc8]

valsalva will also worsen a HCM murmur for the same reason

 

[knuckles]

well almost. valsalva will increase afterload, but in effect have the same effect as standing, regarding the intensity of the murmur.

 

[turkeyjerky]

well almost. valsalva will increase afterload, but in effect have the same effect as standing, regarding the intensity of the murmur.

no, vasalva decreases preload, s/t increased intrathoracic pressure. it's all about venous return baby

 

[knuckles]

I thought it caused blood pressure to increase, increasing afterload. Haha, wahtever. thanks