Interpreting duplex waveforms
In this video, we'll take a look at how duplex waveforms can be obtained in segments throughout the leg, and identify the critical clues that will help you to determine the location and degree of a stenosis.
Doppler waveform analysis plays a fundamental part in the evaluation of peripheral arterial disease. In this video, from our Ultrasound Masterclass: Arteries of the Legs course, we'll take a look at how duplex waveforms can be obtained in segments throughout the leg, and identify the critical clues that will help you to determine the location and degree of a stenosis.
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Duplex waveforms are obtained segmentally throughout the leg and compared for degradation. They're correlated with velocities to confirm a stenosis. The concept of ABI doppler phasicity or peaks and pits holds true for duplex waveforms, tri phasic looks and sounds tri phasic. Still, the difference is with duplex you can see the vessel and can confirm it is widely peyten.
It also records the waveform on a velocity scale which helps grade the percentage of stenosis. However, if there is a stiffening and degradation of phases city, you can image the area and tell if there is plaque buildup or if it is due to wall calcification. Loss of phases city occurs in stages. Each stage represents a different severity of the disease.
These are clearly seen on duplex and categorized as priests the gnosis, interest in gnosis and post gnosis waveforms. The technologist will begin at the level of the common femoral artery or CFA and continue to move distally down the leg to thoroughly evaluate all the main arteries. Similar to AB eyes, multi phasic waveforms are normal.
If there is a blockage in the leg, tri phasic waveforms can usually be obtained only proximal to a significant stenosis. Here, there are tri phasic waveforms at the CFA. This also indicates normal aorta iliac inflow because the CFA is distal to it. arteries distal to a significant stenosis will not be tri phasic. Further down the leg at the mid superficial femoral artery or SFA.
The waveforms are still multi phasic which indicates normal flow. However, at the popliteal artery, this waveform is produced. Compare the normal CFA tri phasic waveform to this interest in gnosis pop a chill waveform and notice a spectral broadening, which is snowy filling of the waveform window due to turbulence produced by this to gnosis.
Also, notice the velocity increased to 576 centimeters a second, compared to 58 centimeters a second previously seen in the SFA. This happens because as the diameter of the lumen decreases from stenosis, the velocity of the blood increases, velocities will be discussed in more detail in less than three. waveforms distal to a significant stenosis are usually monophasic.
The area below the baseline on this waveform is simply phasic vein Doppler interference which is blood flow in the veins. Compare this patient's ABI test to the duplex the dampened monophasic ankle waveforms and abnormal indices suggested gnosis but it doesn't give a location the duplex confirms the blockage location is in the popliteal artery.
Occasionally in duplex a Doppler bruery occurs. This is from the vibration of a vessel that is severely stuck notic if this is seen, but the velocities are not elevated, keep searching nearby as the vibration is usually coming from a stenosis.