tet spells and knee-chest

[Faisal Vali]

[this may be a double post - i apologize, i'm still figuring out my news
reader]

Can someone please explain to me why the knee-chest position helps when
dealing with tet spells in cyanotic tetralogy of fallot patients?

What I've been told is that it tends to increase systemic resistance -
thus decreasing the R->L septal shunt, and encouraging pulmonary flow.

I guess I don't see the physiology behind the knee-chest position
increasing the systemic resistance?

(Does it increase venous return? Is it some form of reflex that triggers
vasoconstriction? Is it increasing intrathoracic pressure (but that
would decrease venous return) and thus increasing arterial tone similar
to the mech behing valsalva?)

thanks in advance!
regards,
Faisal Vali

[Dr. Andrew B. Chung, MD/PhD]

Faisal Vali wrote:

> [this may be a double post - i apologize, i'm still figuring out my news
> reader]
>
> Can someone please explain to me why the knee-chest position helps when
> dealing with tet spells in cyanotic tetralogy of fallot patients?

It increases peripheral vascular resistance.

>
>
> What I've been told is that it tends to increase systemic resistance -
> thus decreasing the R->L septal shunt, and encouraging pulmonary flow.
>

That would be correct.

>
> I guess I don't see the physiology behind the knee-chest position
> increasing the systemic resistance?
>

The femoral arteries get "kinked" at the groin.

>
> (Does it increase venous return? Is it some form of reflex that triggers
> vasoconstriction? Is it increasing intrathoracic pressure (but that
> would decrease venous return) and thus increasing arterial tone similar
> to the mech behing valsalva?)
>

See above.

>
> thanks in advance!
> regards,
> Faisal Vali

You're welcome. Glad to help.

Humbly,

Andrew

--
Dr. Andrew B. Chung, MD/PhD
Board-Certified Cardiologist
http://www.heartmdphd.com