VT Non-Invasive Testing Procedures 3 — Questions and Answers
Question 1: Which duplex ultrasound finding is characteristic of vertebral artery steal syndrome (subclavian steal)?
- Antegrade high-velocity flow in the ipsilateral vertebral artery
- Complete reversal of flow direction in the ipsilateral vertebral artery (Correct answer)
- Bidirectional venous flow in the basilar artery
- Absence of diastolic flow in the contralateral vertebral artery
Correct answer: Complete reversal of flow direction in the ipsilateral vertebral artery
Subclavian steal causes complete flow reversal in the ipsilateral vertebral artery as it supplies the arm via retrograde flow.
Question 2: In segmental pressure testing of the lower extremity, a pressure gradient of 30 mmHg between adjacent cuffs is considered:
- Normal physiologic variation
- Borderline and requires clinical correlation only
- Significant, suggesting stenosis at that level (Correct answer)
- Artifactual due to cuff placement error
Correct answer: Significant, suggesting stenosis at that level
A gradient ≥20–30 mmHg between adjacent cuff levels indicates hemodynamically significant disease at that segment.
Question 3: When performing a venous duplex exam of the saphenofemoral junction (SFJ), what maneuver is used to provoke reflux?
- Active dorsiflexion of the foot
- Valsalva maneuver or manual calf compression with release (Correct answer)
- Elevation of the limb above heart level
- Hyperventilation to increase venous tone
Correct answer: Valsalva maneuver or manual calf compression with release
Valsalva maneuver or manual compression-release augments venous flow and unmasks reflux at the SFJ when reversed flow exceeds 0.5 seconds.
Question 4: Which finding on transcranial Doppler (TCD) is MOST consistent with vasospasm following subarachnoid hemorrhage?
- MCA mean flow velocity < 80 cm/s
- MCA mean flow velocity > 120 cm/s with Lindegaard ratio > 3 (Correct answer)
- Absent diastolic flow in the basilar artery
- Symmetrical flow velocities bilaterally
Correct answer: MCA mean flow velocity > 120 cm/s with Lindegaard ratio > 3
MCA velocity >120 cm/s and Lindegaard ratio (MCA/ICA) >3 distinguish vasospasm from hyperemia.
Question 5: A non-compressible vessel with an ABI of 1.4 is MOST likely due to:
- Severe atherosclerotic stenosis
- Normal athletic conditioning
- Medial arterial calcification (Mönckeberg sclerosis) (Correct answer)
- Acute arterial thrombosis
Correct answer: Medial arterial calcification (Mönckeberg sclerosis)
Medial calcification makes vessels incompressible, falsely elevating ABI >1.30; toe-brachial index (TBI) should be used instead.
Question 6: During renal artery duplex scanning, which PSV threshold is MOST commonly used to suggest hemodynamically significant renal artery stenosis (>60%)?
- >100 cm/s
- >180 cm/s (Correct answer)
- >250 cm/s
- >400 cm/s
Correct answer: >180 cm/s
A renal artery PSV >180 cm/s with a RAR (renal-to-aortic ratio) >3.5 suggests ≥60% stenosis.
Question 7: What is the PRIMARY advantage of using photoplethysmography (PPG) over standard segmental pressures in diabetic patients?
- PPG measures venous capacitance more accurately
- PPG detects skin perfusion and is unaffected by medial calcification (Correct answer)
- PPG provides real-time arterial wall stiffness data
- PPG can differentiate acute from chronic occlusions
Correct answer: PPG detects skin perfusion and is unaffected by medial calcification
PPG measures skin blood flow optically and is not affected by vessel wall calcification that falsifies cuff pressure readings.
VT Non-Invasive Testing Procedures 3
Which duplex ultrasound finding is characteristic of vertebral artery steal syndrome (subclavian steal)?