Squatting maneuver (murmurs & TOF)

[sozme]

Is this correct?

Squatting Maneuver

· Tetralogy of Fallot
** Increases AFTERLOAD by increasing SVR (increases pressure in the left circulation) à right-to-left shunt switches to left-to-right, relieves cyanosis

· Mitral or tricuspid valve prolapse (with or without regurgitation)
** Decreases venous compliance of leg veins à increases VENOUS RETURN
** Makes MVP/regurgitant murmurs SHORTER and moves them closer to S2


(Maneuvers that decrease LV volume such as sitting, standing, or strain of the Valsalva maneuver cause the click to move closer to S1. Maneuvers that increase LV volume move the click toward S2).

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[ljc]

ToF: Correct, but I would go one step further in saying that the left to right shunt forces more blood through the lungs, which is why cyanosis is relieved.

Mitral Prolapse: First off, squatting INCREASES venous return (you're contracting a huge amount of muscle all at once by squatting, thus pushing all the blood in your legs back to the heart). Standing up would have the opposite effect (all the blood in your legs/lower abdomen will suddenly want to sink downward when you stand, away from the heart, thus less venous return). Valsalva strain decreases venous return as well, because you're basically clamping down on the IVC and preventing any blood from flowing through it.

With that said, squatting would increase venous return = bigger LV = LATER MVP murmur. Standing or valsalva = less venous return = smaller LV = earlier murmur. Here's a slide on this topic from one of our lectures.

I think that covers it. Hopefully my understanding is correct.

 

[megaman123]

The way I like to think about it is rapid squatting causes increased preload, which would create a later onset click in MVP (pressure on chordae tympani in the ventricle causes delayed ballooning - almost as if pulling it down the leaflets) and decrease murmur for hypertrophic cardiomyopathy (I think about it like the edge of the ventricle don't clap together).
However with continued squatting, I believe the continued contraction of muscles causes increased afterload, which helps decrease the R-L shunt with the ToF patients allowing more to go into the pulmonary circulation.
Correct me if I am wrong.

 

[solitarius]

A related issue is why wouldn't squatting also increase afterload in the prolapse scenario? Theoretically, it would resist some outflow and redirect blood faster into the LA and closer to S1?

 

[megaman123]

"Rapid" squatting causes increase in preload (think of it like the initial burst). Continued squatting involves continued contraction of muscles like hand gripping. With kids with ToF staying in the squatting position helps increase afterload and allows less R to L shunting.
The cause of the later onset of the MVP is what I like to think of is pressure in the LV on the chorda tympani pulling the leaflets down. Therefore, an increase in afterload would cause an increase in pressure and volume in the LV thus pulling the leaflets down. You can think of preload the same way. An increase in preload would increase the LV pressure/volume again pulling the leaflets down. The only way to get an earlier onset of click is by decreasing the volume in the LV and that is via the valsalva maneuver/standing up.

 

[cbrons]

Rapid squatting squeezes large leg veins (reduces capacitance) --> increased venous return.