VT ABI & Segmental Pressure Testing 2 — Questions and Answers
Question 1: A diabetic patient has an ABI of 1.4. What is the most appropriate next diagnostic step?
- Proceed with angiography immediately
- Perform toe-brachial index (TBI) measurement (Correct answer)
- Diagnose as normal and discharge
- Order CT scan of the lower extremities
Correct answer: Perform toe-brachial index (TBI) measurement
An ABI ≥1.4 indicates non-compressible vessels due to medial calcification, common in diabetics, so TBI is used as an alternative measure of perfusion.
Question 2: Segmental pressures show a gradient of 30 mmHg between the high thigh and above-knee cuff. What does this suggest?
- Aortoiliac disease
- Superficial femoral artery disease (Correct answer)
- Popliteal artery disease
- Tibial artery disease
Correct answer: Superficial femoral artery disease
A pressure drop of ≥20–30 mmHg between the high thigh and above-knee segments localizes disease to the superficial femoral artery.
Question 3: Which waveform finding at the femoral level, combined with a normal ABI at rest, most strongly suggests iliac inflow disease?
- Triphasic waveform
- Monophasic waveform (Correct answer)
- Biphasic waveform with high peak velocity
- Absent diastolic flow
Correct answer: Monophasic waveform
A monophasic waveform at the femoral level indicates damped inflow, suggesting proximal (iliac) stenosis even when resting ABI appears borderline normal.
Question 4: When performing ABI, why is the higher of the two brachial systolic pressures used as the denominator?
- To minimize false-positive results for PAD (Correct answer)
- To account for subclavian artery stenosis in one arm
- Because the dominant arm always has higher pressure
- To standardize results across different labs
Correct answer: To minimize false-positive results for PAD
Using the higher brachial pressure as the denominator avoids overestimating the ABI and reduces false-positive PAD diagnoses when arm pressures differ.
Question 5: A patient's exercise ABI drops from 0.95 at rest to 0.55 immediately post-treadmill. What is the interpretation?
- Normal physiologic response
- Hemodynamically significant PAD unmasked by exercise (Correct answer)
- Artifact from improper cuff placement
- Venous occlusion causing pressure drop
Correct answer: Hemodynamically significant PAD unmasked by exercise
A post-exercise ABI drop of ≥0.15–0.20 from baseline confirms hemodynamically significant PAD that was not apparent at rest.
Question 6: Which cuff placement produces the 'high thigh' pressure in a standard four-cuff segmental study?
- At the inguinal ligament level (Correct answer)
- Immediately above the patella
- At the mid-femoral level
- Just below the inguinal ligament
Correct answer: At the inguinal ligament level
The high-thigh cuff is placed at the inguinal ligament level to assess common femoral and proximal SFA inflow pressure.
Question 7: In a patient with rest pain and an ABI of 0.3, which ankle pressure range is most consistent with critical limb ischemia?
- Greater than 80 mmHg
- 50–80 mmHg
- 30–50 mmHg
- Less than 50 mmHg (Correct answer)
Correct answer: Less than 50 mmHg
Critical limb ischemia is typically defined by an ankle pressure below 50 mmHg or toe pressure below 30 mmHg in the presence of rest pain or tissue loss.
VT ABI & Segmental Pressure Testing 2
A diabetic patient has an ABI of 1.4.
What is the most appropriate next diagnostic step?