CCI Vascular Hemodynamics Principles 4 — Questions and Answers
Question 1: The parvus et tardus waveform pattern distal to a stenosis is characterized by:
- Elevated peak systolic velocity and steep upstroke
- Reduced peak velocity and prolonged systolic acceleration time (Correct answer)
- Reversed diastolic flow and high pulsatility
- Normal velocity with spectral broadening only
Correct answer: Reduced peak velocity and prolonged systolic acceleration time
Parvus (small amplitude) and tardus (slow rise) describes the dampened, delayed waveform seen downstream from a significant proximal stenosis.
Question 2: Which vessel wall property primarily determines the capacitance function of the arterial system?
- Intimal thickness
- Medial smooth muscle compliance (Correct answer)
- Adventitial collagen density
- Endothelial shear stress response
Correct answer: Medial smooth muscle compliance
The elastic recoil of medial smooth muscle allows large arteries to store and release energy, buffering pulsatile flow.
Question 3: In venous hemodynamics, which maneuver is used to assess valve competence during duplex ultrasound?
- Valsalva maneuver (Correct answer)
- Hyperventilation
- Passive leg elevation
- Breath-hold at end inspiration
Correct answer: Valsalva maneuver
Valsalva maneuver increases intra-abdominal pressure and abolishes normal venous flow; reflux upon release indicates valve incompetence.
Question 4: Portal hypertension is most commonly associated with which Doppler finding in the portal vein?
- Increased phasic respiratory variation
- Reversal of portal venous flow (hepatofugal) (Correct answer)
- High-velocity turbulent portal inflow
- Absence of portal venous signal
Correct answer: Reversal of portal venous flow (hepatofugal)
Hepatofugal (away from the liver) portal flow reversal is a hallmark of severe portal hypertension caused by cirrhosis.
Question 5: Which equation directly describes the relationship between pressure gradient, flow, and resistance?
- Bernoulli's equation
- Ohm's law analog (ΔP = Q × R) (Correct answer)
- Continuity equation
- Laplace's law
Correct answer: Ohm's law analog (ΔP = Q × R)
The hemodynamic analog of Ohm's law states that pressure gradient equals flow multiplied by resistance (ΔP = Q × R).
Question 6: A toe-brachial index (TBI) is preferred over ABI in diabetic patients because:
- Toe arteries are larger and easier to compress
- Medial calcification of tibial arteries causes falsely elevated ABI (Correct answer)
- Toe pressure is always lower in normal individuals
- Doppler cannot detect tibial artery signals in diabetics
Correct answer: Medial calcification of tibial arteries causes falsely elevated ABI
Medial calcification in tibial arteries of diabetic patients makes them non-compressible, producing falsely elevated ABI values.
Question 7: Which type of plaque morphology on ultrasound is associated with the highest embolic stroke risk?
- Homogeneous echogenic (calcified) plaque
- Heterogeneous plaque with hypoechoic (lipid-rich) component (Correct answer)
- Smooth, uniformly hyperechoic plaque
- Thin fibrous cap with posterior shadowing
Correct answer: Heterogeneous plaque with hypoechoic (lipid-rich) component
Heterogeneous plaques with hypoechoic (lipid-rich or hemorrhagic) components are more vulnerable to rupture and embolization.
CCI Vascular Hemodynamics Principles 4
The parvus et tardus waveform pattern distal to a stenosis is characterized by: