How does squatting help during Cyanotic or tet spells ?

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In Cyanotic spells in congenital heart diseases, patient gets relieved when in sitting position or squatting position.
How does it help?
What is the mechanism and logic behind it?

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1 Answer


In Tetralogy of Fallot, the Right Ventricular pressure exceeds the Left Ventricular pressure, resulting in a right to left shunt. Squatting increases systemic vascular resistance which causes Left Ventricular pressure to temporarily rise above Right Ventricular pressure, thereby producing a temporary reversal of the shunt. Therefore, when the patient squats during the cyanotic spells, more blood enters the lungs for oxygenation.

answered Mar 7, 2014 by admin Doctor of Medicine (9,909 points)
commented Jun 9, 2014 by Oyetunde Taiwo
nice answer, thanks