Mitral prolapse click question

[notarealname]

Hey guys, got a question for you! I was reading GT today the stuff about mitral prolapse click didn't make sense to me I hope someone can explain the logic behind it. Here is what it says in GT:

Decrease preload would make the mitral prolapse click move closer to S1.

Increase preload would make the click move closer to S2.

My understand is that the preload is the filling of the heart, I think less filling of the ventricle would means less systolic pressure and would cause the mitral valve to prolapse slower and move the click closer to S2, not moving the click closer to S1 like the GT said. Can anyone help?

Thanks!

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[PMPMD]

Hey guys, got a question for you! I was reading GT today the stuff about mitral prolapse click didn't make sense to me I hope someone can explain the logic behind it. Here is what it says in GT:

Decrease preload would make the mitral prolapse click move closer to S1.

Increase preload would make the click move closer to S2.

My understand is that the preload is the filling of the heart, I think less filling of the ventricle would means less systolic pressure and would cause the mitral valve to prolapse slower and move the click closer to S2, not moving the click closer to S1 like the GT said. Can anyone help?

Thanks!

Decreased preload decreases tension on the chordae tendinae (decreased distance from papillary muscle to annulus), which allows the mitral leaflets to prolapse earlier in systole.

 

[Phlame217]

I think of it this way:

Its the pressure difference between the left ventricle and the left atrium that determines when the valve will prolapse.

With decrease preload (less pressure in the left atrium) the high pressure ventricle will be able to push the valve back sooner so its closer to S1 (start of systole).

With increase preload (more pressure in left atrium) the high pressure ventricle will be met with more resistance in the left atrium and so it takes more pressure to cause a prolapse and is closer to S2 (end of Systole).

 

[PMPMD]

Also see this thread

 

[notarealname]

OK thanks guys, it seems there are more than one explanation to this thing. I came up with my own explanation please help to see if it make sense.

Whenever I do something like this I try to start from the basic.

S1 is the sound coming from closing of the mitral and tricuspid valves
S2 is the sound coming from the closing of the aortic and pulmonary valves

If mitral valve prolapse sound is heard closer to the S1, it basically means the sound is heard closer to the tricuspid valve. And preload basically means pressure in the right atrium.

Therefore a decrease of preload means less pressure therefore less filling in the right atrium, therefore less filling of the right ventricle and less pressure generated, therefore S1 sound will be heard a bit slower. And the interval between S1 and S2 would be the same. Though the interval of S2 to the next S1 will be prolonged. This delayed S1 due to less preload would have moved Mitral prolapse sound closer to it. But there is another factor involved that is the speed of closing of the valves, I will explain that in the end.

An increase in preload would mean increase in filling of the Right ventricle, more pressure when right ventricle contract, faster closing the tricuspid valve it would mean S1 is faster. But a mitral valve prolapse at a slower speed than the closing of an intact tricuspus valve, therefore the time between S1 and mitral valve prolapse is delayed much longer compared with the case of decreased preload.

To make this simpler to understand consider tricuspid valve and mitral valve as two parachutes, the parachutes get expanded during ventricular contraction. The tricuspid valve is a good parachute that expand quickly when ventricle contract, the mitral valve is a bad parachute that don't expand well, it is slower and it leaks when the ventricle contract.

The trick is that the two parachutes get affected differently at different pressure. The good parachute (the tricuspid valve) get a great effect when the ventricular pressure drops, and opens much slower, but the bad parachute (the mitral valve) don't get much effect because it is already bad, so a decrease of ventricular pressure doesn't slow it down as much. The result is great decrease of tricuspid valve closure time (slower S1), and a slight decrease of mitral valve closure. All these would put the S1 (from tricuspid valve) closer to mitral valve prolapse sound during decrease of preload...

I hope I made some sense here.