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Stent graft treatment of graft VA stenosis

Posted By Jeffrey Hoggard, Thursday, September 8, 2016

The following case is from the RENOVA  trial and illustrates some caveats of stent graft treatment for VA stenosis.

 

A  65 YO woman  with  ESRD,  DM, HTN, dyslipidemia, obesity  presented to the access center with a dysfunctional left upper arm Brachial Basilic bridge graft placed  4 months ago. She started hemodialysis one month after the graft was placed.  

 

 

Pertinent access history included  high venous pressures,   decreased access flows and prolonged bleeding at her cannulation sites.  On exam , the AVG was  pulsatile and there was a high pitched bruit at the VA.  Angiogram revealed a severe stenosis at the VA and absence of other inflow or outflow  stenoses. She was randomized in the RENOVA trial to the balloon PTA only arm.

 

Fig 1: shows redundant graft and  probably a  90 degree angle of anastomosis of graft with outflow basilic vein.  The VA is 100%  stenosed with retrograde flow to collaterals. 

 

Fig 2:  A wire would not cross the VA stenosis due to the acute angulation and lack of leverage using multiple guiding catheters.  Therefore, the basilic vein was cannulated using ultrasound guidance at the elbow and a glidewire was threaded  straight across the stenosis.

 

Fig 3 and 4: An 8 mm Conquest balloon was positioned across the VA occlusion and angioplastied to 30 atm. There was vascular rupture which was controlled and resolved easily  with prolonged balloon angioplasty. Note the absence of retrograde and collateral flow once the true outflow path was re-established.

 

Fig 5: Subsequently a  second glidewire  was  threaded across the VA from the graft access and angioplasty  with the 8 mm balloon over this second wire  was  repeated in the VA.   

 

Fig 6:  Post angioplasty angiogram.  Outflow basilic vein is approximately 8 mm in diameter and appears healthy. The graft was a straight 6 mm ePTFE.

 

Fig 7: Post angioplasty angiogram with graft wire and basilic wire removed from the VA.   Note the graft angulation with the VA returning.

 

 

The patient returned to the access center 2 months later with prolonged bleeding and high venous pressures.

 

 

Fig 8: The VA stenosis has reoccurred.

 

Fig 9: After balloon PTA with an 8 mm balloon, the VA stenosis was repaired with an  8 mm x 30 mm Flair stent graft.

 

This patient  completed her  2 year Renova follow up without any further interventions.  She continues to dialyze with  this graft and is approaching her 6 year anniversary of the graft placement.  Her VA has remained patent and never required further intervention since the Flair stent graft placement.  She has required 4 subsequent endovascular  interventions – all intragraft stenoses treated with balloon pta.

 

 

 

We now have 3 randomized controlled trials  published in peer-reviewed journals  demonstrating superior patency at the target lesion( VA) and in the access circuit  using  stent graft  treatment  vs balloon PTA  for VA stenosis;  the  Flair pivotal trial and the Renova trial  (Flair stent graft)  and  the Revise trial (Viabahn stent graft) .   Graft VA stenosis has been  recognized as a recurrent problem for 30 years and  yet we have been hypnotized by the immediate cosmetic success   of balloon angioplasty.   Bare metal stents were tried and  have never been proven any better than balloon angioplasty. These 3 stent graft trials  demonstrate that we have a better tool in our  tool box to treat graft VA stenosis.  I highly recommend dialysis access  interventionists read these published trials.   One does not need to be a statistician to recognize the superior results of stent grafting VA stenosis.  Much of the criticisms of this new treatment strategy has economic origins; and I agree that economics of stent graft use in the outpatient access centers are germaine.  However as we transition from a fee-for-service   to a  bundled , accountable care , pay-for- performance paradigm  of reimbursement ,  we need to  know which tool in the tool box is going to give us the best patency.  It behooves us to familiarize ourselves with how to deploy these stent graft devices ( read the IFU)  and the results they can provide our patients.  My experience is that  instent restenosis of a  stent graft  in  the VA is rare.

 

These are some caveats from the case presented. 

 

1.She  received a Flair stent graft  on her second visit in the trial and required no further interventions over the 2 year follow up. She was evaluated in the balloon only ( intention- to- treat) control cohort. Therefore her excellent results which i attribute to the Flair stent VA stenosis repair actually  contributed to  better target and access circuit patency as primary endpoints for the  balloon angioplasty  control  group.

 

2. It was fortuitous that she was randomized to the balloon only arm. A 90 degree angle of anastomosis was a contraindication to Flair stent deployment at randomization.  She ended up getting stent graft treatment and my experience is that the Flair stent stiffness is an excellent  "fix" for 90 degree angles at the VA.  Just as the wire helped straighten the redundant portion of graft and the acute angle,  i think the stent graft can  help  " straighten"  the angle and provides theoretically more laminar flow.   She had an obese upper arm and the graft has to go from superficial cannulation zone  to a very deep VA; i see this frequently in obese upper arm AVGs.

 

3. The retrograde and collateral flow is eliminated or "jailed off" with this covered stent treatment. This was a non-issue in the trial outcomes. My experience is also that this does not cause any clinical problems. i have never seen an arm swell after a VA stent graft treatment ( forearm or upper arm graft location). 

 

4. When does one stent graft the VA? The trials would indicate that primary treatment of VA stenosis  provides best patency. Even if one does not agree and wishes to try balloon angioplasty first, i would encourage interventionists to consider stent graft treatment for those VA stenoses that reoccur in under 3 months.  My dialysis patients with  av graft access do not have loss of their grafts  due to VA stenosis anymore ( with stent graft repair);  repetitive cannulation  injury  and pseudo-aneurysm degeneration in the graft body are now the leading causes of graft loss and abandonment for my patients.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Wesley A. Gabbard says...
Posted Friday, September 9, 2016
Hi Jeff,
Although I totally agree with your premise, we now have three studies that show that stent-grafts are superior to pta at the venous anastomosis, do you not think part of her problem was due to surgical technique. Firstly, it looks like the venous anastomosis was created near a valve and a branch point. Second, the 90 degree end-to-side anastomosis is obviously going cause turbulence. If you look at Dr. Ross' sutureless venous anastomosis using a hybrid graft, basically an end-to-end anastomosis with the stent-graft at the end of the graft. This technique would be helpful for obese patients as the axillary vein only has to be cannulated to create the venous anastomosis. This also may allow the axillary or basilic vein to be cannulated more proximally where it is larger. This brings me to my second thought. I am impressed that you could land a 3cm length Flair at the venous anastomosis. It also appears that the stent is over-sized for the vein where is coapts to the walls. Lastly, I have been told so much about radial force, but I find the stiffness of the Flair mostly conforms the vein to its shape instead of vice versa. I think the Flair can be detrimental based only how the vein moves with flexion-extension of the arm and shoulder. Also, under-sizing the proximal end of the stent actually improves blood flow and decreases turbulence (flow studies by Dr. Ross). As I see it, there is no real role for coapting the stent to the vessel wall. The shape of the flared-tip Flair looks nice as a selling point, but functionally it is not useful. Overall, I still want to say that I agree with Jeff. Maybe, the venous anastomosis could be angioplastied at the first intervention (although, if this patient was not in a study, one of my indications for stenting is when it takes a great deal of effort to cross the stenosis), but stent-graft placement at the venous anastomosis should occur early when there is dysfunction of the graft.

Unfortunately, I cannot get the figures to attach.

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Wesley A. Gabbard says...
Posted Friday, September 9, 2016
Click link below for figures.
http://www.asdin.org/resource/resmgr/Gabbard_2.pdf
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James Wynn says...
Posted Friday, September 9, 2016
Perhaps a surgical perspective will be helpful. I would assert that the venous anas was created WAY too inferiorly in the arm, thereby essentially committing the surgeon to a 90 deg graft/vein anastomosis. The good news is that, when this access eventually begins to fail, running another PTFE graft segment to the upper basilic/lower axillary vein above the Flair stent will be an excellent salvage procedure. I agree w/ stent-graft placement for venous anas stenosis as well, and employ Viabahn prostheses for recurrent stenosis/thrombosis and for all anastomotic lesions w/ a persistent waist post-angioplasty.
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