Your answer
(B) is correct!
- One French (F) =1/3 mm. Thus, the diameter
of the 6 F catheter is equal to 2 mm. The saphenous graft just distal
to the subtotal lesion is approximately 2 1/2 time the size of the catheter
or 5 mm in diameter. Many experienced cardiologists can "eye ball"
an estimate of the vessel diameter. However, quantitative digital measurements
of the vessel should be employed when there is any doubt or when the
operator does not have vast experience.
- In this case the cardiologist chose a 4.5 mm
PTCA balloon with a compliance curve that would achieve an expected
diameter of 4.75 mm at high inflation pressures. The ideal PTCA balloon
size would have been a 4.75 mm, expandable to 5.0 mm but this was not
available.
- A 5.0 mm PTCA balloon (expandable to 5.25 mm)
may have been acceptable but not chosen for fear of dissecting the aorto-graft
junction and extending this to the ascending aorta. It was felt that
one could always upsize to a 5 mm PTCA balloon if subsequently needed.
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