Step I Valsalva/Squatting

[Master Deep]

Hey guys,
Im really confused about MVP. I know that MVP murmur is supposed to be enhanced by Valsalva, but In FA it says it is enhanced by squatting and hand grip. I thought that Valsalva and Squatting were opposite.. Valsalva decreased Venous return/preload which enhances the murmur.
But then how does squatting which does the exact opposite ( increase venous return/preload) also enhance the murmur. Maybe im missing something?
Thanks

 

[sgod34]

According to WIKI:

In contrast to most other heart murmurs, the murmur of mitral valve prolapse is accentuated by standing and valsalva maneuver (earlier systolic click and longer murmur) and diminished with squatting (later systolic click and shorter murmur).

Both valsalva maneuver and standing decrease venous return to the heart thereby decreasing left ventricular diastolic filling (preload) and causing more laxity on the chordae tendineae. This allows the mitral valve to prolapse earlier in systole, leading to an earlier systolic click (i.e. closer to S1), and a longer murmur. Hand grip maneuver increases total peripheral resistance (afterload) and therefore increases back pressure on the mitral valve resulting in a more intense murmur without changing the timing of the systolic click.