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Doppler interpretation

Discussion in 'General Issues and Discussion Forum' started by lcp, Jun 8, 2008.

  1. lcp

    lcp Active Member


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    gday all, just hoping someone can point me in the right direction regarding correct reading of the doppler printouts. learnt it way back when in uni, but cant remember a lot.
    thanks in advance
    paul
     
  2. jos

    jos Active Member

    1. Look for tall sharp systolic peak. Any broadening of the peak (into a 'hill' shape) can indicate occlusion proximally. This may be supported by Hx vascular surgery/high cholesterol etc
    2. Look for the downstroke into diastole - this shows that the arteries are still elastic and able to recoil. Abscence indicates possible calcification of arterial walls, as they are not able to recoil very well and hence the downstroke will not be there on the trace.
    3. Look for the constant distance between the peaks (also evident audibly) to show regular beats - surprising how many people have arrthymia of varying degrees.

    Hope this helps!
     
  3. lcp

    lcp Active Member

    thanks jos thats actually a pretty sweet interpretation, thanks mate much appreciated
    paul
     
  4. Bobthefoot

    Bobthefoot Welcome New Poster

    Hello Jos,

    Where does the reflective wave and the late systolic peak fit in? In a patient with PAD the diastole is going to be missing but presumably there will be a much lower wave with a 2nd low peak??

    I'm new to all this, so would be grateful for any advice. Bob
     
  5. Adrian Misseri

    Adrian Misseri Active Member

    When I was at uni, we were always told to look for a regular triphasic waveform, sharp peaks, good volume and a steady rhythm. Bear in mind though, that we've all had different amounts of doppler training, and there's a great deal of variation depending on where exactly you place the probe, how you align the probe, the quality of the instrumentation, experience using the doppler etc. One of my local vascular surgeons suggested to myself that the doppler waveform is not so important, but the ABI/TBI tells much more about the state of the arterial supply than the doppler will in our clinical settings.
     
  6. Mart

    Mart Well-Known Member

    There was a fair depth to discussion at

    http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=10424

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  7. Asher

    Asher Well-Known Member

    Hi all,

    Please help!

    Does the dicrotic notch appear on a normal (no arterial disease) Doppler waveform?

    Rebecca
     
  8. Mart

    Mart Well-Known Member

    Rebecca

    I think that you are confusing doppler waveforms with PVR waveforms.

    Theoretically, a normal ankle doppler waveform the diastolic event is seen as a reverse flow in response to peripheral resistance (provided your probe is positioned correctly in relation to axis of blood flow).

    In PVR waveforms the direction of flow is not measured, simply the change in volume, if peripheral resistance is normal this is seen as a dicrotic notch.

    If peripheral resistance is low (compensatory vasodilation in response to decreased flow to maintain O2 levels) ; reverse flow will be absent in Doppler waveform, dicrotic notch will be absent in PVR waveform and systolic peak will be delayed in both because of increased vessel compliance.

    Hope that helps

    Cheers


    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    Phone [204] 837 FOOT (3668)
    Fax [204] 774 9918
    www.winnipegfootclinic.com
     
  9. Asher

    Asher Well-Known Member

    Yes Martin, that does help. Many thanks!

    Rebecca
     
  10. Asher

    Asher Well-Known Member

    Martin, I have a number of questions that remain unanswered that you may be able to help me with:

    1. PPG measures blood flow just under the skin surface. Is this blood flow in the capillaries or both capillaries and arterioles? This is basically an anatomy question.

    2. Doppler qualitative waveform analysis for arteries is essentially about triphasic, bispasic or monophasic. Is it the same for PPG waveform analysis? Or is PPG waveform analysis just about amplitude of the waveform? What amplitude (numerical) is ideal? Or is it more about shape (how narrow / broad the waves are)?

    3. My Doppler mentions the 'mean blood velocity'. Is this an important measure? My understanding thus far is that the velocity will vary according to the angle the probe is to the artery and therefore you probably can't use the measure as being particularly meaningful.

    Thanks in advance for anything you can give me.

    Rebecca
     
  11. Mart

    Mart Well-Known Member


    Hi Rebecca

    Here’s my understanding, no claims to expertise so please bear that in mind.

    PPG works by directing light through the skin and measuring the reflected energy via a photosensor which converts this into a visible signal. The amplitude of the signal is proportional to the reflected energy which is proportional to volume of RBCs which absorb energy and is pulsatile because of pressure (hence volume) changes within the same measured vessels. On that basis my assumption is that the signal represents blood volume NOT flow but I may be wrong. Hence the waveform approximates to PVR which also measures effects of changes in blood volume. Volume measured would depend on output of LED, thickness of epidermis, quality of transducer/skin coupling, vasoconstrictive state (temp, medications, inflammation) etc. My assumption would be that vessels examined would vary according to what falls within penetration depth and sensitivity of system which might also vary. This is why this method is only capable of qualitative not quantitative assessment.

    Doppler gives qualitative information like you mention according to the characteristic of forward- reverse – forward pattern of a healthy wave form.

    I believe most Doppler units utilise 2 modes.

    In one the Y axis displays average reflected frequency: remember doppler signal is analysed as frequency shift caused by sound wave reflections being compressed or elongated according to velocity and direction of RBCs. The frequency measured is spectral because according to site insonated there is variability in velocity at any instant in time of individual RBCs (laminar flow) according to relationship of RBCs to vessel wall and obstacles, angle of beam (probe) incidence and possible turbulence from stenosis. The instrument will average frequencies measured and usually create a zero line which corresponds to frequency of probe. Therefore signal above line is shifted higher or conversely below line lower than probe frequency. Key point is that this averaging is done to everything caught and reflected within beam path. Therefore venous flow, collateral arterial flow, and probe motion can alter waveform. When performing the exam it is necessary to account for this by searching the probe around, testing for venous flow and seeing how this affects the waveform when necessary. With this understanding you can make some generalised deductions about the rate of change of flow (slope) which is affected by vessel compliance and altered pressure dynamics in post stenotic or collateral vessels. Look at the systolic upstroke time and monophasic shape which may be flattened and chaotic. Do you have the Unetixs book because this is well covered and my knowledge is based mostly on this text?

    In the other mode there is a Y axis greyscale depiction of the various frequencies reflected rather than averaging, this creates a different waveform which doesn’t have a zero line or obviously average frequencies and has a different quality (and dicrotic notch because of no zero line). It gives potentially more info but the impression I have is that it is less widely used with the advent of more sophisticated and affordable pulsed dopper imaging which provides vastly superior quantitative exam.

    I think mean velocity is incorporated so that quantitative waveform analysis can be done. PI (peak to peak pulsatility index) is the ratio of the difference between max and min peak velocity to mean velocity. Again I think this measure has fallen out of favour because of lack of evidence of reliability but cannot substantiate this, I may be wrong there.

    hope this helps too.

    cheers

    Martin
     
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