Mechanism of squatting in TOF – MCQ – Answer

Mechanism of squatting in TOF – MCQ – Answer

Children with tetralogy of Fallot often get relief on squatting after exertion. What is the mechanism of benefit? Correct answer: a) Increase in afterload of the left ventricle and decrease in right to left shunting

Squatting causes compression of the femoral arteries and increase in the afterload of the left ventricle. In addition to this, compression of the lower limbs reduces the preload to the right ventricle. It also cuts off the severely unsaturated blood returning from the lower limbs. The associated abdominal compression pushes more saturated blood in inferior vena cava to the right heart. The higher oxygen saturation in the inferior vena cava is caused by renal venous return. Renal vein has the highest oxygen saturation in the body because renal blood flow is mostly for filtration and not for gas exchange.

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