RVT - Registered Vascular Technologist Post-Intervention and Grafts Questions and Answers 1 — Questions and Answers
Question 1: A patient undergoes duplex surveillance one year after an endovascular aortic aneurysm repair (EVAR). The aneurysm sac has increased in diameter by 7 mm since the last study, but no endoleak can be visualized with color or spectral Doppler. This condition is best described as:
- Graft limb thrombosis
- A Type II endoleak
- Endotension (Correct answer)
- A Type III endoleak
Correct answer: Endotension
Endotension, also referred to as a Type V endoleak, is defined as the continued expansion of the aneurysm sac by more than 5 mm without a detectable endoleak on imaging studies. [12, 21] It is believed to be caused by pressure transmission through the graft material or an occult leak that is below the resolution of the imaging modality. [19]
Question 2: During surveillance of a prosthetic femoropopliteal bypass graft, a focal area of color aliasing is noted mid-graft. The peak systolic velocity (PSV) within this segment is 320 cm/s. The PSV in a normal-appearing graft segment just proximal to this area is 150 cm/s. What is the velocity ratio (Vr), and what is the most likely interpretation?
- Vr = 1.7; Mild (<50%) stenosis
- Vr = 2.1; Significant (≥50%) stenosis (Correct answer)
- Vr = 0.47; Suggests proximal disease
- Vr = 2.5; Suggests impending occlusion
Correct answer: Vr = 2.1; Significant (≥50%) stenosis
The velocity ratio (Vr) is calculated by dividing the highest PSV at the stenosis (320 cm/s) by the PSV in a normal proximal segment (150 cm/s), which equals 2.13. A Vr ≥ 2.0 is a widely accepted criterion indicating a hemodynamically significant stenosis of 50% or greater in a peripheral bypass graft. [14]
Question 3: Which of the following sonographic findings is a key component of the 'Rule of 6s' for assessing the maturation of a newly created arteriovenous fistula (AVF) for hemodialysis access?
- Fistula depth from the skin surface must be greater than 6 mm
- Minimum fistula diameter must be at least 6 cm
- Volume flow should be greater than 600 mL/min (Correct answer)
- The fistula should be at least 6 cm from the antecubital fossa
Correct answer: Volume flow should be greater than 600 mL/min
The 'Rule of 6s' is a clinical guideline to assess AVF maturation. The sonographic criteria include: a minimum vein diameter of 6 mm, a vein depth from the skin of no more than 6 mm, and a measured volume flow of at least 600 mL/min. [5, 7, 9]
Question 4: A patient is being evaluated one year after undergoing carotid artery stenting (CAS). Duplex ultrasound of the stented segment reveals a peak systolic velocity (PSV) of 350 cm/s and an end-diastolic velocity (EDV) of 145 cm/s. These findings are most consistent with:
- Normal, expected velocities within a carotid stent.
- Severe (≥70-80%) in-stent restenosis. (Correct answer)
- Mild (<50%) in-stent restenosis.
- Stent occlusion with collateral flow.
Correct answer: Severe (≥70-80%) in-stent restenosis.
Velocity criteria for stenosis are higher within a stent compared to a native artery. While criteria can vary slightly by institution, a PSV greater than 300-340 cm/s and an EDV greater than 140 cm/s are commonly used to identify a severe (≥70% or ≥80%) in-stent restenosis. [1, 2, 8]
Question 5: What is the expected spectral Doppler waveform morphology in a normally functioning, mature lower extremity reversed saphenous vein bypass graft that is supplying the ankle and foot?
- High-resistance, multiphasic (triphasic or biphasic) (Correct answer)
- Low-resistance, monophasic with high diastolic flow
- A 'tardus parvus' waveform
- A continuous, non-pulsatile venous-like signal
Correct answer: High-resistance, multiphasic (triphasic or biphasic)
A bypass graft assumes the hemodynamic characteristics of the vascular bed it supplies. Since the arteries of a resting lower extremity are a high-resistance bed, a normal graft waveform should be high-resistance, meaning it will be multiphasic (triphasic or strongly biphasic) with sharp systolic upstroke and minimal diastolic flow. [23]
Question 6: During an EVAR follow-up ultrasound, flow is detected originating from patent lumbar arteries that perfuses the aneurysm sac in a retrograde fashion. This finding is the classic presentation of which type of endoleak?
- Type I
- Type II (Correct answer)
- Type III
- Type IV
Correct answer: Type II
A Type II endoleak is defined as retrograde flow into the aneurysm sac from collateral branch vessels, most commonly the lumbar arteries or the inferior mesenteric artery. [26, 28, 29] Type I is a leak at the graft attachment sites, Type III is a graft defect, and Type IV is due to graft porosity. [27]
RVT - Registered Vascular Technologist Post-Intervention and Grafts Questions and Answers 1
A patient undergoes duplex surveillance one year after an endovascular aortic aneurysm repair (EVAR).
The aneurysm sac has increased in diameter by 7 mm since the last study, but no endoleak can be visualized with color or spectral Doppler.
This condition is best described as: