CCI Vascular Hemodynamics Principles 2 — Questions and Answers
Question 1: Which hemodynamic principle explains why blood velocity increases when a vessel narrows?
- Pascal's principle
- Continuity of flow equation (Correct answer)
- Laplace's law
- Poiseuille's law
Correct answer: Continuity of flow equation
The continuity equation states that flow volume is conserved, so velocity must increase when cross-sectional area decreases.
Question 2: In a stenotic vessel, the pressure gradient across the lesion is primarily determined by:
- Vessel wall compliance
- Flow velocity and lesion geometry (Correct answer)
- Red blood cell deformability
- Plasma viscosity alone
Correct answer: Flow velocity and lesion geometry
The pressure gradient across a stenosis depends on flow velocity squared and the geometric characteristics of the narrowing.
Question 3: The ankle-brachial index (ABI) in a normal individual should be approximately:
- 0.5–0.7
- 0.7–0.9
- 0.9–1.3 (Correct answer)
- 1.3–1.5
Correct answer: 0.9–1.3
A normal ABI ranges from 0.9 to 1.3; values below 0.9 suggest peripheral arterial disease.
Question 4: Which waveform characteristic indicates high distal vascular resistance in a peripheral artery?
- Monophasic waveform with absent reverse flow
- Triphasic waveform with prominent reverse component (Correct answer)
- Continuous forward flow throughout diastole
- Broad systolic peak with low pulsatility
Correct answer: Triphasic waveform with prominent reverse component
A triphasic waveform with a prominent reverse-flow component in early diastole is the hallmark of high distal resistance.
Question 5: What does a markedly elevated pulsatility index (PI) in a renal artery most likely indicate?
- Renal artery stenosis proximal to the sample site
- Elevated renal vascular resistance (Correct answer)
- Arteriovenous fistula within the kidney
- Normal renal perfusion
Correct answer: Elevated renal vascular resistance
An elevated PI in the renal artery reflects increased downstream vascular resistance, often seen in chronic renal disease.
Question 6: Which parameter best distinguishes a hemodynamically significant carotid stenosis from a non-significant one on Doppler?
- Common carotid artery diameter
- Peak systolic velocity in the ICA (Correct answer)
- Resistive index of the ECA
- Diastolic notch depth
Correct answer: Peak systolic velocity in the ICA
Peak systolic velocity in the internal carotid artery is the primary Doppler criterion for grading stenosis severity.
Question 7: Turbulent flow in a blood vessel is most likely to occur when the Reynolds number exceeds:
- 200
- 500
- 2000 (Correct answer)
- 5000
Correct answer: 2000
Reynolds numbers above approximately 2000 are associated with the transition from laminar to turbulent flow.
CCI Vascular Hemodynamics Principles 2
Which hemodynamic principle explains why blood velocity increases when a vessel narrows?