VT Dialysis Access Surveillance 2

Question 1

Which Doppler parameter is most commonly used to define hemodynamically significant stenosis in a dialysis AVF?

Accepted Answer

Peak systolic velocity ratio >2:1 at stenosis

Answer

A peak systolic velocity ratio greater than 2:1 across a stenotic segment indicates hemodynamically significant stenosis in AVF surveillance.

Question 2

A hemodialysis patient's access flow drops from 1,200 mL/min to 550 mL/min over two months. What is the most appropriate next step?

Accepted Answer

Refer for fistulogram and intervention

Answer

A >25% decrease in access flow below 500 mL/min warrants urgent referral for fistulogram and possible angioplasty to prevent thrombosis.

Question 3

During duplex surveillance of an AVG, you identify a peak systolic velocity of 450 cm/s within the graft body. The proximal inflow velocity is 120 cm/s. What does this indicate?

Accepted Answer

Intragraft stenosis with velocity ratio >3:1

Answer

A velocity ratio of 450/120 = 3.75:1 far exceeds the 2:1 threshold, confirming significant intragraft stenosis.

Question 4

Which finding on duplex ultrasound is most suggestive of venous outflow stenosis in a dialysis AV fistula?

Accepted Answer

Pulsatile waveform throughout the fistula

Answer

Outflow stenosis causes increased resistance, converting the normally low-resistance venous waveform to a pulsatile pattern throughout the fistula.

Question 5

What is the recommended minimum access flow threshold below which AVF thrombosis risk is substantially elevated?

Accepted Answer

500 mL/min

Answer

Access flow below 500 mL/min in an AVF is associated with significantly increased risk of thrombosis and is an intervention threshold.

(VT) Vascular Technician Certification Practice Test

(VT) Vascular Technician Certification Practice Test

VT Dialysis Access Surveillance 2