ARDMS SPI Hemodynamics and Vascular Flow Principles 2 — Questions and Answers
Question 1: The pulsatility index (PI) is calculated as:
- PSV / EDV
- (PSV − EDV) / mean velocity (Correct answer)
- EDV / PSV
- (PSV + EDV) / PSV
Correct answer: (PSV − EDV) / mean velocity
The Pulsatility Index = (Peak Systolic Velocity − End Diastolic Velocity) / Mean Velocity, providing a measure of downstream resistance.
Question 2: Which Doppler finding is most indicative of a hemodynamically significant proximal arterial stenosis?
- Increased peak systolic velocity at the stenosis site
- High-resistance waveform distal to the lesion
- Monophasic, low-resistance tardus-parvus waveform distal to the stenosis (Correct answer)
- Normal triphasic waveform distal to the lesion
Correct answer: Monophasic, low-resistance tardus-parvus waveform distal to the stenosis
A tardus-parvus (slow rise, small amplitude) waveform distal to a significant stenosis reflects the damped, delayed transmission of the pulse through the obstruction.
Question 3: Poiseuille's Law states that blood flow through a vessel is most sensitive to changes in which parameter?
- Vessel length
- Blood viscosity
- Vessel radius (Correct answer)
- Pressure gradient
Correct answer: Vessel radius
Flow is proportional to the fourth power of radius; halving the radius reduces flow 16-fold, making radius by far the most powerful determinant of vascular resistance.
Question 4: In a normal hepatic vein Doppler waveform, the waveform is expected to be:
- Monophasic and continuous
- Biphasic with antegrade flow only
- Triphasic with both antegrade and retrograde components reflecting cardiac pulsatility (Correct answer)
- High-resistance triphasic arterial pattern
Correct answer: Triphasic with both antegrade and retrograde components reflecting cardiac pulsatility
Normal hepatic veins transmit right atrial pressure changes, producing a triphasic waveform with S, D, and A waves including a brief retrograde A wave.
Question 5: The spectral window in a normal arterial Doppler waveform represents:
- The area of aliased velocities
- The clear area below the spectral envelope indicating organized laminar flow (Correct answer)
- Turbulent flow within the vessel
- Reverse flow component
Correct answer: The clear area below the spectral envelope indicating organized laminar flow
The clear spectral window below the waveform envelope reflects the narrow, uniform velocity distribution of laminar flow where few cells travel at intermediate velocities.
Question 6: Elevated end-diastolic velocity (EDV) in an arterial waveform typically indicates:
- High downstream vascular resistance
- Arterial vasospasm
- Low downstream vascular resistance (high diastolic demand) (Correct answer)
- Proximal arterial occlusion
Correct answer: Low downstream vascular resistance (high diastolic demand)
High EDV indicates continued forward flow throughout diastole, reflecting low downstream resistance from vasodilation, as seen in low-resistance organs like the kidney or brain.
ARDMS SPI Hemodynamics and Vascular Flow Principles 2
The pulsatility index (PI) is calculated as: