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Old 02-27-2014
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Question Hand grip and HCM

Why does the murmur of HCM decrease with hand grip?
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Old 02-27-2014
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Okay this is my understanding. Correct me if I am wrong.
Because of increased afterload or increased systemic vascular resistance, the blood flow across MV will decrease. As a result of which there will be more blood in the ventricle. This pushes the hypertrophied IVS to one side away from the anterior MV leaflet relieving the obstruction and decreasing murmur intensity.
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Old 02-27-2014
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Quote:
Originally Posted by Oncology_freak View Post
Okay this is my understanding. Correct me if I am wrong.
Because of increased afterload or increased systemic vascular resistance, the blood flow across MV will decrease. As a result of which there will be more blood in the ventricle. This pushes the hypertrophied IVS to one side away from the anterior MV leaflet relieving the obstruction and decreasing murmur intensity.
What you are thinking makes perfect sense thanks. I agree.
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Old 02-27-2014
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Default Reason for decreased murmur intensity in HCM

Hi,

http://imageshack.com/a/img822/7347/w961.jpg

In the above diagram, due to increased thickness of interventricular septum, the anterior leaflet of mitral valve comes closer to it.

Think of a car cruising on a road filled with fallen leafs, the faster the car moves, the the faster the leafs move along with the car as it goes along the road.

Now, apply this situation to the HCM patient's heart,
The blood in the Left ventricle is the car, and the anterior leaflet of the Mitral valve as the leafs on the road.

So, if blood passes out from LV into Aorta at a faster rate, then the ant leaflet comes more closer to the IVS, this increases the intensity of the Systoloc ejection murmur.

When the hands are clenched, the TPR is increased, due to this the ejection rate of blood (car speed) is slower, and as mentioned above, the ant. leaflet of mitral valve, doesn't comes closer to IVS, this decreases the murmur intensity.

Hope this helps
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Old 02-27-2014
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Increased afterload ==> more blood in the LV (just like oncology_freak said) and also increase preload both will increase left ventricular size.

Increased afterload (handgrip) or increasing preload (lying down for example) both cause increased left ventricular size which would attenuate the degree of outflow obstruction by pushing the IV septum which will in turn, reduce the intensity of the murmur.

Reducing preload (standing, phase II valsalva etc.) would decrease the left ventricular size and increase the intensity of the murmur.
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Old 03-15-2014
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Ok guys
1.why should the intensity also decrease in aortic stenosis with hand grip?
2. Why shd the murmur intensity decrease during valsava ( decrease venous return) in Mitral valve prolapse?
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