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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 back 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
The correct

ccc
Q=VxA

yes CCCC

C!

Yes all right..C is correct..Flow has increased 7-fold, indicating a decrease in
cross-sectional area by a factor of 7. This would be caused by an obstruction, not an
aneurysm.
Choice A is incorrect, because a coronary artery aneurysm would produce an increase in
cross-sectional area rather than a decrease.
Flow has increased 7-fold, indicating a decrease in vessel diameter, thus choices B and
D are incorrect.

Thanks for the questions 2c2bd
However I think your analysis of the answer may not be correct.
It is velocity that is being measured and not flow.
Velocity is inversely proportional to the total cross sectional area and that's why the answer is C and not the flow as flow is inversely proportional to the radius to the fourth power.