RVT Post-Intervention and Grafts 2 — Questions and Answers
Question 1: Which PSV ratio across a graft stenosis is most consistent with a hemodynamically significant (>50%) lesion?
- PSV ratio >2.0 (Correct answer)
- PSV ratio >1.5
- PSV ratio >1.0
- PSV ratio >3.5
Correct answer: PSV ratio >2.0
A peak systolic velocity ratio greater than 2.0 at the stenosis versus the adjacent graft segment indicates a hemodynamically significant stenosis of greater than 50%.
Question 2: On duplex surveillance of a PTFE above-knee femoropopliteal bypass graft, a focal PSV of 380 cm/s with a PSV ratio of 3.8 is found. What is the most appropriate next step?
- Refer for angiography or intervention (Correct answer)
- Repeat surveillance in 3 months
- Start anticoagulation and recheck in 1 month
- Document as normal variant for PTFE grafts
Correct answer: Refer for angiography or intervention
A PSV >300 cm/s with a ratio >3.5 indicates a severe stenosis (>70%), warranting urgent referral for angiographic evaluation and possible intervention.
Question 3: A vein graft exhibiting low-velocity, monophasic waveforms throughout its length without a focal stenosis most likely represents which condition?
- Impending graft failure due to inflow disease or low-flow state (Correct answer)
- Normal postoperative hemodynamics
- Graft arteriovenous fistula
- Successful graft remodeling
Correct answer: Impending graft failure due to inflow disease or low-flow state
Uniformly low velocities with monophasic waveforms throughout a graft suggest poor inflow or high outflow resistance, placing the graft at risk for thrombosis.
Question 4: During carotid endarterectomy surveillance, which finding at the endarterectomy site is MOST concerning for restenosis requiring intervention?
- ICA PSV >300 cm/s with ICA/CCA ratio >4.0 (Correct answer)
- ICA PSV of 160 cm/s with mild spectral broadening
- ICA PSV of 200 cm/s with ICA/CCA ratio of 2.5
- Mild intimal thickening with PSV <125 cm/s
Correct answer: ICA PSV >300 cm/s with ICA/CCA ratio >4.0
An ICA PSV >300 cm/s combined with an ICA/CCA ratio >4.0 indicates severe (>70%) post-CEA restenosis, which typically warrants intervention.
Question 5: A patient presents 2 years after renal artery stent placement. Duplex shows an intrarenal acceleration time of 0.09 seconds with a tardus-parvus waveform. What does this suggest?
- Significant in-stent restenosis proximal to the sampling site (Correct answer)
- Normal post-stent hemodynamics
- Renal vein thrombosis
- Acute tubular necrosis
Correct answer: Significant in-stent restenosis proximal to the sampling site
An acceleration time >0.08 seconds with a tardus-parvus pattern indicates a significant proximal stenosis damping flow to the renal parenchyma, suggesting in-stent restenosis.
Question 6: After endovascular aneurysm repair (EVAR), a type II endoleak is identified. What is its hemodynamic source?
- Retrograde flow from patent lumbar or inferior mesenteric arteries (Correct answer)
- Inadequate proximal seal at the aortic neck
- Inadequate distal seal at the iliac landing zone
- Graft fabric porosity
Correct answer: Retrograde flow from patent lumbar or inferior mesenteric arteries
Type II endoleaks arise from retrograde flow into the aneurysm sac via collateral vessels such as lumbar arteries or the inferior mesenteric artery.
Question 7: Which duplex finding best distinguishes a pseudoaneurysm from a perigraft hematoma at a femoral access site?
- To-and-fro flow pattern ('yin-yang' sign) on color Doppler (Correct answer)
- Absence of internal color flow
- Hyperechoic collection adjacent to the artery
- Calcification at the margin of the collection
Correct answer: To-and-fro flow pattern ('yin-yang' sign) on color Doppler
A pseudoaneurysm communicates with the artery via a neck, producing the characteristic bidirectional to-and-fro ('yin-yang') color Doppler pattern inside the sac.
RVT Post-Intervention and Grafts 2
Which PSV ratio across a graft stenosis is most consistent with a hemodynamically significant (>50%) lesion?