Increasing blood pressure AORTA?!

[StayingFocused]

I don't know if this was already asked, I searched for it and couldn't find it. But its this question from the MCAT it says:

Coarctation of the aorta, a congenital defect in which the aorta is narrowed, would cause which of the following if left untreated?

A.
Decreased pressure in the pulmonic circuit

B.
Increased pulse pressure

C.
Decreased pressure in the lower limbs

Correct Answer

D.
Decreased venous valve function



I thought if you increased arterial resistance you increase overall blood pressure in the body. How is the aorta different?

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[neurodoc]

Coarctation refers to a constriction in the aortic arch. If the constriction occurs distal to the take off of the supply to the upper extremities, the pressure in the lower extremities will be decreased. The coarctation can result also in asymmetric BP in the upper extremities, if it is between the take offs to the right and left arms...in this case the BP will be less in the arm supplied distal to the coarctation, usually the left arm.

 

[TieuBachHo]

I thought if you increased arterial resistance you increase overall blood pressure in the body. How is the aorta different?

By arterial resistance, you mean arterial constriction that increases BP? Aortic constriction occurs before the oxygenated blood being pumped through out the body. If there is a clog upstream, downstream will suffer (lowering pressure). On the other hand, arterial constriction occurs after/at the distal end of branching out, so the effect is inverse of the proximal end as in the coarctation. This seems to be a relatively straight forward question, I am not sure if that is what you are asking for?