CCI Vascular Hemodynamics Principles 3 — Questions and Answers
Question 1: Which of the following best describes the effect of arterial compliance on pulse wave velocity?
- Higher compliance increases pulse wave velocity
- Lower compliance increases pulse wave velocity (Correct answer)
- Compliance has no effect on pulse wave velocity
- Compliance only affects diastolic pressure
Correct answer: Lower compliance increases pulse wave velocity
Stiffer (less compliant) arteries transmit the pressure wave faster, resulting in higher pulse wave velocity.
Question 2: The resistive index (RI) is calculated as:
- (PSV − EDV) / PSV (Correct answer)
- (PSV − EDV) / EDV
- (PSV + EDV) / mean velocity
- EDV / PSV
Correct answer: (PSV − EDV) / PSV
RI = (peak systolic velocity − end diastolic velocity) / peak systolic velocity, ranging from 0 to 1.
Question 3: In a patient with a large arteriovenous fistula, which hemodynamic change is expected in the feeding artery?
- Increased RI with absent diastolic flow
- Decreased RI with high diastolic flow (Correct answer)
- Monophasic waveform with reverse flow
- Normal triphasic waveform
Correct answer: Decreased RI with high diastolic flow
An AV fistula creates a low-resistance pathway, producing low RI and elevated diastolic flow in the feeding artery.
Question 4: Which hemodynamic phenomenon causes spectral broadening distal to a stenosis?
- Laminar flow restoration
- Post-stenotic turbulence (Correct answer)
- Decreased red cell velocity
- Increased plasma viscosity
Correct answer: Post-stenotic turbulence
Post-stenotic turbulence produces a wide range of velocities that fill in the spectral window, causing spectral broadening.
Question 5: A patient has an ABI of 0.6 at rest. According to standard classification, this corresponds to:
- Normal arterial perfusion
- Mild PAD
- Moderate PAD (Correct answer)
- Severe PAD
Correct answer: Moderate PAD
An ABI of 0.4–0.69 is classified as moderate peripheral arterial disease with significant flow limitation.
Question 6: What is the primary reason collateral vessels have higher resistance than the native artery they replace?
- Collaterals have thicker walls reducing lumen size
- Collaterals are smaller in diameter and longer in length (Correct answer)
- Collaterals lack smooth muscle
- Collaterals are composed of veins
Correct answer: Collaterals are smaller in diameter and longer in length
Poiseuille's law dictates that resistance is proportional to length and inversely proportional to radius to the fourth power, making small, long collaterals high-resistance.
Question 7: On duplex ultrasonography, which finding is most specific for renal artery stenosis >60%?
- Renal artery PSV > 180 cm/s
- RAR (renal-to-aortic ratio) > 3.5 (Correct answer)
- RI < 0.5 in intrarenal arteries
- Renal length discrepancy > 1 cm
Correct answer: RAR (renal-to-aortic ratio) > 3.5
A renal-to-aortic ratio greater than 3.5 is highly specific for hemodynamically significant renal artery stenosis.
CCI Vascular Hemodynamics Principles 3
Which of the following best describes the effect of arterial compliance on pulse wave velocity?