mitral valve prolapse

[rkim1]

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i'm stumped. in mitral valve prolapse, you get a click and murmur. depending on the left ventricular end diastolic volume, the click and murmur can move closer or farther from S1. more volume moves it farther and less volume moves it closer. why isnt it the other way around? it seems that if there's more volume, it will take a shorter amount of time to reach the pressure at which the valve prolapses. either there's a really simple explaination for this or i should put off the boards until august....or both. anyways, i would appreciate any input...

 

[bizcuit241]

It is just physics. It takes less time to generate enough force to overcome the pressure against a smaller volume as opposed to a larger volume. I guess in terms of cardiovascular physiology this could mean that the isometric contraction phase would be shorter.

 

[viper]

I will second that - here is what I have annotated in FA - god knows where it's from now (probably goljan)!

"Maneuvers that cause click/murmur to come closer to S1 are those that decrease vol in ven. so systole occurs faster (standing up, valsalva, anxiety). Closer to S2 - increase volume in ventricles (lying down (increased venous return), sustained clenching of fists (increase afterload))