Step I Does squatting dec afterload or inc preload?

[MudPhud20XX]

FA15 page 278 says that squatting increases preload by increasing venous retrun, but I think it rather increases afterload. In TOF, kids squats to increase TPR, thus to increase afterload right? So is this a typo? Or does squatting lead to both dec in afterload and inc inc preload?

 

[slz1900]

It may increase afterload but I believe that the main reason that patients with TOF benefit from squatting is actually not due to afterload but due to an increase in MAP which is a result of increased cardiac output.

Increasing preload with squatting leads to increased preload -> Frank Sterling mechanism -> increased CO. MAP = CO * SVR and SVR actually doesn't change much with squatting.

Here is a paper that talks about it: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC483991/

 

[worldbeater]

Squatting in Tetralogy of Fallot increases systemic vascular resistance (World Q). If you are increasing SVR, you are increasing venous return to the heart, which would make me think preload would increase.

 

[Jabbed]

The act of squatting increases preload (i.e., compressing venous vasculature in the legs). Prolonged squatting increases afterload. ToF patients derive benefit from increased afterload as it minimizes the right to left shunting of blood from the RV through the VSD and out the aorta.