vallia
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A patient complaining of chest pain with exercise is evaluated by
cardiac catheterization. The left anterior descending (LAD) branch of
the coronary artery is visualized but the contrast angiography is poor
. A Doppler-tipped catheter is inserted and the blood velocity is observed
to increase transiently from 10 cm/sec to 70 cm/sec and then decrease bac
k to 10 cm/sec as the probe passes a particular location in the artery
. What was the cause of these changes in velocity measurements?
A. A coronary artery aneurysm with a cross-sectional area 1/7th the size of the native artery
B. A coronary artery aneurysm with a cross-sectional area 7 times greater than the native artery
C. A coronary artery obstruction with a cross-sectional area 1/7th of the size of the native artery
D. A coronary artery obstruction with a cross-sectional area 7 times greater than the native artery
please explain, thanks
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| mediocre
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A >, i will give my xplanation if i am right,thanx
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| oldkidontheblock
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d
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| MD_toronto
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Ans C.
Velocity is inversly proportional to cross section ( 7 velocity = 1/1/7).
If velocity increased 7 times there is equivalent 1/7 decrease in cross section area (Ans C).
I have eliminated A and B because anuerysm is not common in coronary arteries. If it was aorta than it's significant to look for A & B.
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| mediocre
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oops ,I take back A
the ans should be C (its a block ofcourse!)
Reason: for haiving a block is clear,d/t--------symptoms of angina
now the other part is physics,Bernollis thorem ,most probably,
or in simpler terms since the same volum of blood has to go thru 1/6 of the space it has to go 6 times as fast ,obviously.
plz ,let us know the correct ans.thanx
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| vallia
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it's c. thanks
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| Leopard
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Velocity of any fluid
V = Q/A
where Q= quantity of fluid passing
A = cross sectional area
So velocity is increased if there is
- Either increase in fluid flow
- or decrease in cross sectional area
Because in the above scenario only cross sectional area is being changed ,so it should reduce by stenosis
Best of luck
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