CCI Vascular Hemodynamics Principles 5 — Questions and Answers
Question 1: In lower extremity arterial occlusion, which collateral pathway most commonly reconstitutes the popliteal artery?
- Lateral circumflex femoral artery
- Geniculate anastomosis around the knee (Correct answer)
- Peroneal communicating branches
- Profunda femoris perforators
Correct answer: Geniculate anastomosis around the knee
The geniculate arteries form an anastomotic network around the knee that reconstitutes the popliteal artery distal to a femoral occlusion.
Question 2: The acceleration time (AT) measured in intrarenal arteries is prolonged when:
- There is an intrarenal arteriovenous malformation
- There is significant proximal renal artery stenosis (Correct answer)
- Renal vein thrombosis is present
- The patient is dehydrated
Correct answer: There is significant proximal renal artery stenosis
Significant renal artery stenosis dampens the waveform, prolonging the time from onset of systole to peak systolic velocity (AT > 70–80 ms).
Question 3: Which hemodynamic change occurs during exercise in a patient with hemodynamically significant PAD?
- ABI increases due to improved cardiac output
- ABI decreases due to inability to raise distal pressure (Correct answer)
- Ankle pressure rises proportionally with brachial pressure
- Collateral flow eliminates the exercise-induced pressure drop
Correct answer: ABI decreases due to inability to raise distal pressure
During exercise, vasodilation increases flow demand but the stenosis limits pressure transmission, causing ankle pressure to fall and ABI to decrease.
Question 4: What does the term 'critical stenosis' refer to in vascular hemodynamics?
- Any stenosis visible on angiography
- The degree of stenosis beyond which resting flow begins to fall (Correct answer)
- Stenosis requiring immediate surgical intervention
- Stenosis associated with plaque ulceration
Correct answer: The degree of stenosis beyond which resting flow begins to fall
Critical stenosis is the threshold (approximately 75% area reduction or 50% diameter reduction) beyond which autoregulatory mechanisms can no longer maintain resting flow.
Question 5: In the venous system, the primary driving force for venous return from the lower extremities during ambulation is:
- Respiratory variation in intrathoracic pressure alone
- Calf muscle pump compressing deep veins (Correct answer)
- Hydrostatic pressure gradient from the foot
- Arterial flow transmitted retrogradely
Correct answer: Calf muscle pump compressing deep veins
The calf muscle pump compresses deep veins during walking, propelling blood proximally and reducing venous pressure in the leg.
Question 6: Which Doppler finding is characteristic of deep vein thrombosis (DVT) in the femoral vein?
- Augmented flow with distal compression
- Absence of phasic respiratory variation and non-compressibility (Correct answer)
- Continuous high-velocity flow with spectral broadening
- Reversed flow during Valsalva maneuver
Correct answer: Absence of phasic respiratory variation and non-compressibility
DVT is diagnosed by non-compressibility of the vein and loss of normal phasic respiratory variation on duplex ultrasound.
Question 7: Mean arterial pressure (MAP) is best approximated by which formula?
- (Systolic + Diastolic) / 2
- Diastolic + (Pulse pressure / 3) (Correct answer)
- Systolic − Diastolic
- 2 × Diastolic + Systolic / 3
Correct answer: Diastolic + (Pulse pressure / 3)
MAP ≈ Diastolic + (1/3 × pulse pressure) because diastole occupies approximately two-thirds of the cardiac cycle.
CCI Vascular Hemodynamics Principles 5
In lower extremity arterial occlusion, which collateral pathway most commonly reconstitutes the popliteal artery?