VT Non-Invasive Testing Procedures 2 — Questions and Answers
Question 1: Which waveform characteristic is MOST associated with a proximal arterial obstruction when assessing a distal vessel?
- Triphasic high-resistance waveform
- Monophasic dampened waveform with loss of dicrotic notch (Correct answer)
- Biphasic waveform with sharp systolic peak
- High-frequency spectral broadening only
Correct answer: Monophasic dampened waveform with loss of dicrotic notch
A proximal obstruction dampens the distal waveform, producing a monophasic pattern with loss of the dicrotic notch and reduced pulsatility.
Question 2: During a lower extremity venous duplex exam, which finding is MOST diagnostic of acute deep vein thrombosis?
- Hyperechoic intraluminal material with partial compressibility
- Anechoic lumen with absence of spontaneous flow and non-compressibility (Correct answer)
- Increased color flow velocity with spectral broadening
- Augmented flow with distal compression only
Correct answer: Anechoic lumen with absence of spontaneous flow and non-compressibility
Acute DVT classically presents as a non-compressible vein with anechoic (echo-free) intraluminal thrombus and absent spontaneous flow.
Question 3: A patient's ankle-brachial index (ABI) is 0.55. Which clinical category does this fall into?
- Normal arterial perfusion
- Mild peripheral arterial disease
- Moderate peripheral arterial disease (Correct answer)
- Severe/critical limb ischemia
Correct answer: Moderate peripheral arterial disease
An ABI of 0.41–0.70 indicates moderate PAD, associated with claudication symptoms.
Question 4: What is the significance of a post-exercise ABI that DECREASES by more than 20% from resting values?
- Normal physiologic response to exercise
- Evidence of hemodynamically significant arterial stenosis (Correct answer)
- Venous insufficiency unmasked by exercise
- Artifact from poor electrode placement
Correct answer: Evidence of hemodynamically significant arterial stenosis
A post-exercise ABI drop >20% confirms hemodynamically significant PAD even when resting ABI is borderline.
Question 5: Which parameter is used to calculate the Resistive Index (RI) in renal duplex ultrasound?
- (PSV − EDV) / PSV (Correct answer)
- (PSV − EDV) / EDV
- PSV / EDV
- EDV / PSV
Correct answer: (PSV − EDV) / PSV
RI = (PSV − EDV) / PSV; values >0.70 suggest increased downstream resistance or intrinsic renal disease.
Question 6: During carotid duplex imaging, an ICA/CCA PSV ratio of 4.2 correlates with which degree of stenosis?
- 50–69%
- 70–79%
- ≥80% (Correct answer)
- Near occlusion
Correct answer: ≥80%
An ICA/CCA ratio ≥4.0 is consistent with ≥80% stenosis per Society of Radiologists in Ultrasound (SRU) criteria.
Question 7: What physiologic principle explains why plethysmographic waveforms become flattened and prolonged with arterial occlusive disease?
- Increased venous reflux proximal to the obstruction
- Reduced pulse pressure and delayed pressure transmission distal to the stenosis (Correct answer)
- Hypervolemia from compensatory collateral flow
- Vasospasm of the venous system
Correct answer: Reduced pulse pressure and delayed pressure transmission distal to the stenosis
Arterial stenosis reduces and delays the pressure wave, resulting in flattened, prolonged plethysmographic waveforms distally.
VT Non-Invasive Testing Procedures 2
Which waveform characteristic is MOST associated with a proximal arterial obstruction when assessing a distal vessel?