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Unlanded Stent

Posted By Harold R. Locay, Friday, September 16, 2016
Updated: Saturday, September 17, 2016

75 y/o Hispanic male with ESRD on dialysis  with a LUA brachial straight graft from 2010. He had an 8x50 Flared Flair stent placed at the venous anastomosis  in 2011, had done well until 2016. He presented to our outpatient vascular access center with elevated venous pressures and prolonged bleeding. Six weeks prior he presented with the same access issues and had in-stent stenosis that underwent PTA with good result. No other pertinent medical history.

On angiogram he was found to have severe  in-stent stenosis (fig. 1). PTA with a 9x4 Conquest was done with full effacement but a residual of greater than 50% was noted. A 9x50 Flared Flair was placed with 10mm overlap of the stents in the non flared section. The stent was deployed slowly but did not seem to flower well all the way back (fig. 2). A 9x4 Conquest was carefully placed to seat the stent, the stent migrated forward but was caught with the balloon (fig. 3). The stent on the balloon was pulled slightly back into the prior stent but could not be well overlapped or seated at that point as it was expanded (fig. 4). The balloon was removed and and a 10x100 Fluency stent was placed, as the Flared Flair stent continued to slowly migrate. The fluency was seated with a 10x4 Conquest and overlapped the original stent and most of the 9x50 Flared Flair stent with a space in between the two. (fig. 5). Final angiogram shows good flow (fig. 6).

 

 

Questions:

1) Should one avoid using a flared stent in a flared stent ?

2) Should one overlap more than the standard 10mm when stenting at the angle of the access (use a longer stent)?

3) Should I just snare/retrieve an unlanded stent ?

4) Should I have just pulled the stent/shaft out when I noticed the stent not flowering well (50% deployed at that point) (placed bareback) ?

  

Thanks

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Wesley A. Gabbard says...
Posted Friday, September 16, 2016
This is such a good case. I found this issue many times when deploying a flared-tip Flair stent. I am not certain if it is the flared end acting as a sail or the deploying device. I found that even shutting down the arterial inflow and deploying only half of the stent, the Flair stents still had a tendency to migrate. But, if you look at Dr. Ross' data on flows, there is really no reason to coapt the stent to the walls of the vein. I would have under-sized a Viabahn stent in the same area and extended into the axillary vein.

I still cannot add figures. So if ASDIN will help, I will submit the figure on under-sizing in the venous outflow from Dr. John Ross.
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Max J. Glaser says...
Posted Saturday, September 17, 2016
Interesting challenge. A few thoughts come to mind. I wonder if your placing a 9mm stentgraft in an 8 mm stentgraft which is inside a perhaps smaller AV graft is the reason the distal half of the 9 mm stentgraft did not expand with deployment. Did the migration of the stentgraft occur while you tried to advance the conquest balloon through it? If so, it raises the question of whether a lower profile balloon might have avoided that. Another thought of mine is that as much I hate using bare metal stents in the access circuit, this may be one time where a larger bare metal stent might be useful to rescue the migrating 9mm stentgraft and pin it to the outflow vein. That would avoid the probable "curtaining" effect you are likely to get with having a 10 mm stentgraft inside the 8 mm stentgraft at the gva. In any case, he is probably best suited to now have a surgical revision hopefully having enough room in the axilla to work with.
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Kevin C. Harned says...
Posted Sunday, September 18, 2016
I agree with Dr Glaser in terms of sizing. I think we often over-estimate the capacity of a stent's radial force to hold open a lesion. In this case, we already had a metal cage (ie, stent) of 8mm, so perhaps the 9mm was a touch too much, esp given the amount of in-stent stenosis present. If we had a way to core-out that ib-stent stenosis and then place the 9mm, I think you would have been fine. Also, perhaps using a 9x10 stent as opposed to the 9x5 would have prevented the migration, though there still likely would have been some incomplete opening in that smaller opening.

Regardless, I applaud your efforts and salvaging the case as you did without having to snare a stent out of the pulmonary artery. Sometimes how we deal with complications are more interesting than the actual case.
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Wesley A. Gabbard says...
Posted Sunday, September 18, 2016
Stents can be over-sized even in the case of in-stent stenosis. I find the Viabahn can many times be placed through an existing stent and used to rupture this stent when using a Conquest balloon. I have ruptured existing Viabahns, Fluencys, Flairs, and bare metal stents using the Viabahn. This can be be done with a Fluency as well, but the uncovered ends can be problematic at times for leak. I usually cover the entire length of the existing stent. I have ruptured prior smaller stents (say, 7-8mm) that I placed with a 10mm or bigger stent. I have seen this at the venous anastomosis and the cephalic arch where the existing stent is now smaller than the access due to normal growth or from in-stent stenosis. The problem with the Flair stent in this situation is that the two layers of PTFE allow this stent to slide quite easily. I actually think the radial force and lack of flexibility are a detriment when trying to deal with the problem shown in this case.
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Wesley A. Gabbard says...
Posted Sunday, September 18, 2016
Go to link below to see slides.
1. Under-sizing the stent into the outflow vein improves graft function"
2. “One-to-one sizing (with wall apposition diverts high velocity blood flow to the vessel wall causing increased sheer stress.

http://www.asdin.org/resource/resmgr/091816_Gabbard.pdf

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