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Old 09-23-2011
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Default Hypertrophic Cardiomyopathy

Can someone explain me that why in Hypertrophic Cardiomyopathy the murmur sound decreases on increase in preload and vice versa.I know that decrease in preload result in increase obstruction but whats the reason behind this?
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Old 09-23-2011
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Interesting... But yes, there are 2 Disease which you will find the vice-versa of what we used to say....

Hypertrophic Cardiomyopathy and Mitral Valve Prolapse.

So, let me see if i can explain it here by text. A murmur due to HCM will increase in intensity with any maneuver that decreases the volume of blood in the left ventricle ( Valsalva maneuver).. this is in HCM there is a increase of the interventricular septum, so the septum is too thick, so when you have increase of Blood flood into the heart the septum by itself is compress on the ventricular wall... and THERE IS NOT space for any valve to move along beside the natural flow, but when there is a DECREASE of the blow flow into the chambers ( ventricles ) the valve gain space to move inside the ventricles and that's why you heart a SOUND!, same pathophysiology for MVP. In fact, it its more complicated than that, but those are in simple words... hope it help to to understand... a bit.
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Old 09-23-2011
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So just to resume,

Others Mumurs are decrease in Valsalva or Increase when patient Squat or lean.

HCM or MVP are all the way the opposite, They increase with Valsalva and Decrease with Squat or leaning foward.

To keep concept Clean:

Squat or leaning foward = Increase TPR, so increase flow into heart.
Valsalva = Decrease Flow going into the heart by manual compression of IVC.
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Old 09-23-2011
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In HCM the enlarged septum is to close to MV.
It is diastolic heart disfunction. (i think of it as heart fails to relax and dilate)
So septum + MV obstruct the outflow (aortic valve) which causes systolic murmur.
Logically to reduce that you need to dilate the LV with larger amount of blood so you would separate septum away from MV and open the outflow.
So increase preload.


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Old 09-23-2011
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Goljan describes it well in his audio lectures, if you have some time.
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Thanks a lot guys.I finally got it indeed goljan really explains it very well in his audios.
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