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    • #36445
      Chrissie Cummins
      Participant

      Hello fellow Vascular sonographers.
      We have had 2 recent cases in our practice of no flow seen in a newly inserted viabhan (covered) stent 2-3hours post op. The patients had evidence of distal flow and good foot pulses. There was no apparent gas interface artefact that is sometimes seen with other grafts. Just wondering if anyone else has encountered this and could maybe throw some light on the reason this is happening

    • #36448
      Stephen Bird
      Keymaster

      Hi Chrissie,

      In my clinical setting I have not encountered viabahn stents so immediately post op,

      The only ones I scan are at least weeks and usually months after placement and in this setting I have not had a problem.

      I agree gas in the surgical field can be a problem, although this should be fairly obvious on the scan,

      I would be looking at the distal end of the graft where it re-enters the native vessels and assess the waveform at this location.

      I would expect a biphasic waveform with good input pressure if the graft is patent.

      If scans are performed in this immediate post op phase here in Adelaide they would be done by the vascular sonographer working directly for the surgeon rather than by a sono like me working in a radiology setting,

      Steve.

      • #36450
        Chrissie Cummins
        Participant

        Just spoke to the GORE rep and got this explanation. Hope it helps others in a similar situatuion

        The graft is microporous and what you are seeing is air inside the ePFTE. It takes a bit for the graft to be ‘wetted in’, up to two weeks.

        Here is ePTFE under an electron microscope (from google), the air is trapped in these tiny gaps, but it poses no risk to the patient or the graft. Over time, the air dissipates and the gals are filled- however I’m not 100% sure if it’s with tissue or fluid. If you like, I can ask the question to my colleagues to see if they know?

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    • #36697
      Stephen Bird
      Keymaster

      That makes perfect sense Chrissie,

      It explains why they are easy to scan when I see them weeks out months after the surgery, and it makes sense why you can not see into the graft in the immediate post op setting,

      It also makes sense why you thought it was a gas issue.

      Thanks so much for enlightening me and everyone else who is enjoying the forum about this.

      It is a great trap for young players and we now know to delay assessment of the graft itself for a while after placement but we also know we can infer graft latency or failure by looking at the waveforms immediately proximal and distal to the graft on the native vessels.

      So good !

      Steve.

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