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GENERAL
GENERAL
interpretation_of_peripheral_arterial_and_venous_doppler_waveforms-_a_consensus_statement_vm2020.pdfSpectral waveform:
Y axis: range of frequency shifts/velocities
Thickness of line represents range of velocities sampled
Low thickness = low range of values, think center of aorta (laminar flow).
X axis: time
Resistive index: (PSV - EDV) / PSV
Represents the resistance of vascular bed DISTAL to interrogated vessel.
If RI <1 = End diastolic flow must be above 0 = forward EDF
Flow from low to high resistance vascular beds -> forward flow decreases -> RI increases
Higher diastolic flow = lower resistance waveform = lower RI
For organs that need constant perfusion (brain, liver, kidneys, placenta)
Lower diastolic flow = higher resistance waveform = higher RI
For organs that need intermittent / on-demand blood supply (femoral, facial, SMA)
ARTERIAL DOPPLER
ARTERIAL DOPPLER
Reporting arterial waveforms:
Direction of flow
Antegrade, retrograde, bidirectional, absent
Phasicity
Multiphasic, monophasic
Resistance
FLOW DIRECTION
PHASICITY
PEAK SYSTOLIC VELOCITY
PEAK SYSTOLIC VELOCITY
Normal peak systolic velocity (PSV) in ultrasound varies by vessel, with general arterial flows decreasing distally (150-175 cm/s in the aorta vs.
40-90 cm/s in limb arteries) and venous flows typically <20 cm/s
ELEVATED PSV
DECREASED PSV
Downstream (distal) stenosis
Compensatory flow, contralateral to an obstruction or severe stenosis.
Physiologic hyperdynamic state in healthy pt
Upstream (more proximal) stenosis
Poor cardiac pump function
Near-total occlusion
RESISTANCE
RESISTANCE
In absence of disease, the diastolic component in the arterial waveform reflects the vasoconstriction present in the resting muscular beds.
HIGH RESISTANCE
Key features:
Sharp upstroke and brisk downstroke +/- diastolic flow reversal.
Can be multi or monophasic.
Normal waveforms in a high resistive bed will display a retrograde (reflected) wave in early diastole.
LOW RESISTANCE
Key features:
Prolonged downstroke in late systole and continuous forward flow throughout diastole.
Monophasic only.
Prolonged diastolic downslope with the presence of pandiastolic flow.
In contrast to intermediate resistance, the low-resistive waveform contains a continuous and prolonged diastolic forward flow without the presence of an end-systolic notch.
INTERMEDIATE RESISTANCE
Key features:
Sharp upstroke and brisk downstroke
End-systolic notch and continuous diastolic forward flow.
In contrast to low resistance, the intermediate resistive waveform contains a rapid deceleration at end systole followed by a diastolic acceleration with continuous forward flow.
The waveform pattern suggests vasodilation and can be the result of exertion (exercise), increased temperature, vasodilator drugs, or a severe arterial obstruction distal to the point of Doppler insonation.
WAVEFORM CHARACTERISTICS
WAVEFORM CHARACTERISTICS
ABNORMAL ARTERIAL WAVEFORMS
ABNORMAL ARTERIAL WAVEFORMS
PSV is the most accurate method of evaluating the degree of arterial stenosis.
PSV is elevated proximal to and at the site of stenosis.
PSV may be decreased distal to a hemodynamically significant stenosis.
Severity of arterial lumen diameter reduction is reflected in continual increase in PSV and EDV velocities to a critical value consistent w a pre-occlusive lesion.
Minimal diameter reduction can result in slight disruption to laminar flow without significant increase in PSV or change in early diastolic reverse flow.
Loss of reverse flow component and transition from a multiphasic to monophasic flow pattern are apparent when a pressure-flow gradient is formed at site of stenosis.
Tardus Parvus
Tardus - slow upstroke; time to peak > 70 ms
Parvus - weak amplitude
The waveform also indicates the location of arterial obstruction.
Delayed systolic upstroke suggests flow-limiting disease proximal to the recording site.
Distal to a stenosis, ischemia in the tissue bed will result in vasodilation and decreased resistance. Additionally, there is a decrease in distal pressure due to the pressure drop across the stenosis. This pressure drop, along with the lower resistance, results in increased diastolic flow throughout the cardiac cycle distal to a stenosis.
Proximal to an occlusion or high-grade stenosis, the resistance will increase. The reflected wave or any antegrade diastolic flow, if normally present, may be reduced or absent and sequential flow-limiting lesions and collateral vessel capacity can affect waveform morphology at a given Doppler sampling location.
<50% STENOSIS
PSV increases slightly but is less than double that in the normal adjacent proximal segment (velocity ratio < 2).
Typically, there is a multiphasic waveform with rapid upstroke and no appreciable increase in diastolic velocity.
Spectral broadening is pansystolic.
50-74% STENOSIS
When arterial lumen is significantly narrowed, a pressure-flow gradient is present at the stenotic site.
PSV increases by more than 100% (velocity ratio > 2) compared to the normal adjacent proximal segment.
The early diastolic reverse flow component is commonly lost (may be residual in a high-velocity state with extensive collateralization) with continuous, pandiastolic forward flow in response to decreased vascular resistance in the distal tissue bed. Spectral broadening is present.
>75% STENOSIS
Severe arterial narrowing results in at least a fourfold increase in PSV (velocity ratio > 4) compared to the normal proximal adjacent segment.
The waveform is monophasic, diastolic velocity may be increased, and a spectral bruit is commonly noted adjacent to the zero-flow baseline.
DISTAL TO FLOW REDUCING STENOSIS
Waveform is monophasic with prolonged upstroke and PSV is decreased.
Spectral broadening is present.
DISTAL TO OCCLUSION
Waveform is dampened and monophasic
PROXIMAL TO OCCLUSION
In the absence of flow-limiting stenosis proximal to the site of Doppler sampling, the waveform is characterized by rapid upstroke and may be high resistive or intermediate resistive.
Area of high-velocity flow b/n an artery and vein is usually seen as area of aliasing on color doppler.
PSEUDOANEURYSM
Flow is bidirectional (to-fro) through the neck or tract of the arterial pseudoaneurysm. The waveform has a rapid systolic upstroke with exaggerated deceleration, and an elongated and prominent reverse flow component.
AVF
Blood flow from a high-pressure artery into a low-pressure vein results in spectral broadening and elevated systolic and diastolic velocities. Continuous forward flow is noted throughout the cardiac cycle.
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