Doppler Waveform Analysis

Created by lanielu44 

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ESP Vascular Ultrasound Review Guide

What are 2 capabilities of Doppler waveform analysis?

-Help confirm diagnosis/approximate location of disease
-Indicate severity of the occlusive process

Limitations of Doppler waveform analysis

-Casts/extensive bandages
-waveforms affected by ambient temperature
-congestive heart failure (dampened waveforms)
-can't discriminate stenosis from occlusion
-technically dependent

Analog doppler velocimetry

Uses a zero crossing frequency meter to display signals graphically on a strip chart recorder

Zero Crossing Frequency Meter

-counts each time the input signal crosses the zero baseline within a time span
-high frequency waves have many oscillations, low frequency waves have few
-Direction of blood flow varies during the cardiac cycle
-Machine estimates the frequencies present in reflected signal and displays them

Drawbacks to Analog (zero crossing) doppler velocimetry:

-Noise
-Less sensitivity
-High velocities are underestimated
-Low velocities are overestimated

What is spectral analysis?

Individual frequencies are displayed by Fast Fourier Transform (FFT) method.

-more commonly used during duplex evaluation
-Time: x-axis; Frequency shift: y-axis

Where are doppler waveforms taken in UE?

Subclavian
Axillary
Brachial (AC fossa)
Radial (wrist)
Ulnar (wrist)

Where are doppler waveforms taken in LE?

CFA
SFA
Popliteal
Posterior Tibial
Dorsalis Pedis
(Peroneal, if necessary)

Potential sources of technical error in doppler waveforms:

-Probe position
-probe motion
-incorrect angle of incidence
-inadequate amt of gel
-excessive pressure on probe tip
-insufficient rest before testing

Features of Triphasic waveform

-rapid upslope
-sharp peak
-rapid downstroke
-flow reversal
-resumption of forward flow
(i.e. UE, LE arteries)

Features of Biphasic waveform

-radid upslope
-sharp peak
-fairly rapid downstroke
-flow reversal
-no resumption of forward flow
(also considered normal in some pts)

Feature of Monophasic waveform

-slow upslope
-rounded peak
-slow downstroke
-no reversal

A ________ signal is often obtained proximal to an obstruction.

monophasic/dampened (pulsatile)

Waveforms proximal to an obstruction are:

monophasic, pulsatile

Waveforms distal to an obstruction are:

monophasic, more steady

(less resistive due to vasodilation)

Normal doppler waveforms post-exercise

-Pre-exercise waveform qualities are
maintained and/or augmented
-No reverse component

(normally just pressures are taken after exercise, not waveforms)

Abnormal doppler waveforms post-exercise

-slow upstroke
-more rounded peak
-slow downstroke
-no reverse component

Analog doppler not capable of portraying velocities less than ______

6cm/sec

Absent doppler signals may suggest:

Occlusion or a pre-occlusive vessel (string sign)

Pulsatility index equation

(P1-P2) / mean freq

What factors are used in Quantitative (number) evaluation of doppler waveforms?

-pulsatility index
-acceleration time

Pulsatility index and Acceleration time both help to differentiate:

Inflow (aortoiliac) disease from outflow (femoral) disease

Acceleration time in arterial obstruction is the:

slowing of time between the onset of systole to the point of maximum peak.

An acceleration time of _______ suggest presence of proximal iliac disease

>133 msec

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