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Old 03-29-2011
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Heart Strong radial but weak ankle pulses!

I was solving Kaplan QBank and I did'nt understand the explanation for the right answer of this question. Can you help me out please??


A 2-year old with uncomplicated coarctation of aorta appears to be in good health. Growth and development are normal. The constriction is located just distal to the subclavian arteries. Pulses in both arms feel unusually brisk; pulses in ankles feel weaker than normal. Which of the following is most likely decreased in this patient??

A. Blood flow in the lower body

B. Blood flow in the upper body

C. Blood pressure in the upper body

D. Vascular resistance in the lower body

E. Vascular resistance in the upper body
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Old 03-29-2011
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Is it A ? Decreased blood flow in the lower body ?
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Thats what even I answered. But it is not the right answer it seems. In kaplan QBank, it mentions D. Vascular resistance in the lower body as the correct answer.
Can anyone explain it to me plzz??
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i hope i am right.....

Coarctation of aorta..will behave as resistance in series.

Properties of resistance in series. Flow is same at all points. The pressure before the resistance increases to overcome the resistance and maintain flow.

P=QR or Q=P/R.

So in the distal segment, the resistance must dec. to maintain flow at the decreased pressure..
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Quote:
Originally Posted by usmle0987 View Post
Thats what even I answered. But it is not the right answer it seems. In kaplan QBank, it mentions D. Vascular resistance in the lower body as the correct answer.
Can anyone explain it to me plzz??
Ah yes, I had it narrowed down to Options A or D. Just couldnt decide which one lol

Well I thought about it and I guess this makes sense. Because there is constriction AFTER the subclavian arteries, there is no obstruction of blood flow for the upper body. However, the constriction causes a drop in blood pressure and therefore low vascular resistance for the lower body.

I think that is right. Im not quite sure but thats what i thought.
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