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Interventional CV Rounds

Coordinator: Dr. Hugo Londero
Moderator: Dr. Raúl Bretal

Case number 1: Complicated Endoprosthesis in an AAA
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We have asked two well known expertise surgeon and interventionist about their opinion to this problem:

Opinion of Dr. Zvonimir Krajcer
Opinion of Dr. Juan C. Parodi
Case Resolution


Opinion of Zvonimir Krajcer, M.D.,
Program Director, Peripheral Vascular Disease Program,
Texas Heart Institute and St’ Luke’s Episcopal Hospital, Houston, TX

This very interesting case illustrates clearly complexities those interventionist faces when performing endoluminal repair of AAA in patients with Ilio-Femoral arterial disease. There are several comments I would like to make regarding this case prior to giving my recommendations regarding the treatment of failure of the Vanguard II stent graft.

The pre-procedural complexities of this case included:

  1. Sharp angulation of the infrarenal aortic neck
  2. Significant rt. External Iliac Artery stenosis
  3. Bilateral occlusion of Superficial Femoral Arteries
  4. In-stent restenosis of the left. Profunda Femoris Artery

The procedural problems included:

  1. Irregularities in the stent graft that required "aggressive" balloon angioplasty of the stent graft and the right Common Iliac Artery.
  2. Residual, 60% right External Iliac Artery stenosis at the completion of the procedure.

Comments related to pre-procedural and procedural findings:

Severe angulations of the infrarenal neck and the iliac arteries frequently pose a problem after stent graft deployment. This may lead to incomplete expansion of the prosthesis, which may cause endoleaks. Incomplete expansion of the stent graft can also lead to obstruction of flow due to bending or kinking of the iliac arteries.

This problem usually requires balloon angioplasty to fully expand the stent graft. Balloon angioplasty, however, can affect the structural integrity of the stent graft. This occurs by disruptions of sutures that attach the graft material to the stent skeleton. The most vulnerable area is the septation of the bifurcated segment of the stent graft.

The great majority of current generation of stent grafts is too rigid to conform well to severe tortuosities of iliac arteries that are frequently encountered in patients with AAA.

It is a common practice after stent graft deployment, when encountering iliac artery occlusive disease to perform balloon angioplasty and stenting. The balloon angioplasty alone can cause intimal dissection that can lead to acute arterial thrombosis. In our experience stenting offers better results and prevents periprocedural and late stent graft thrombosis. In tortuous iliac arteries with occlusive disease the stents of choice are self-expandable stents. They conform better to the tortuosities of the iliac arteries and prevent arterial kinking that can lead to thrombosis.

The left Profunda Femoris instent restenosis was likely due to deformity of the stent, which was due to external compression ("crush") of the stent. For this reason we routinely use only self-expandable stents in the areas of the vascular system that are susceptible to external compression. This is particularly important for patients that have only one vessel supplying the lower extremity as was present in this patient.

The post-procedural problems included:

  1. Thrombosis of the right Iliac limb of the stent graft
  2. Right External Iliac Artery stenosis

The late (six-month) follow-up problems included:

  1. Exaggerated expansive movement of the graft material
  2. Disruption of the integrity of the stent graft with excessive motion and migration of the stent elements

Comments related to the post-procedural and six-month follow-up problems:

It is evident from the angiographic imaging at six-month follow-up that the integrity of the stent graft is impaired. This is evident by exaggerated motion of the graft material and separation of the stent elements. This was most likely due to disruption of the sutures that attached the graft material to the stent elements. This stent graft design consists of endo-skeleton. When disruption of sutures occurs the graft material that is on the outside of the stent is no longer supported. This exposes the graft to unusually high surface tension that makes it susceptible to disruptions and eventual failure of the stent graft.

It is possible that the original insult to the integrity of the stent graft could have occurred at the time of the deployment and balloon angioplasty. The Fogarty embolectomy four days after the procedure is, however, the more likely event that has affected the stent graft integrity. Unfortunately, the manufacturers of the stent grafts for endoluminal exclusion of AAA have not designed nor have they adequately tested these devices to determine if they can tolerate the "aggressive" use of angioplasty balloons and mechanical embolectomy devices.

Comments regarding treatment of structural failure of the Vanguard II stent graft for endoluminal exclusion of AAA:

Since the structural integrity of this stent graft is compromised this patient is at risk of AAA expansion and rupture. To avoid this complication he will have to undergo another endovascular or open surgical repair of his AAA. Because of his co-morbid conditions another attempt to repair his defect with endoluminal methods is a reasonable alternative. The final decision will ultimately depend on patient’s desire and interventionist’s options and abilities.

Since the structural disruption of this stent graft is located in the bifurcated segment it is unlikely that placing an aortic cuff or the iliac limb cuff will resolve the problem. In my opinion the simplest endovascular solution to this patient’s problem is a placement of an Aorto-Uni-Iliac stent graft and placement of a stent graft occluder device in the contralateral iliac limb. The angiographic images demonstrate that the length of the infra-renal neck is sufficient to accommodate the placement of the Aorto-Uni-Iliac device. In instances when the infra-renal neck is too short the device with a bare stent design for suprarenal anchoring is of benefit. A Femoro-Femoral bypass should follow this at the same time. In this patient we would prefer to place Aorto-Uni-Iliac stent graft through left femoral approach, since the left iliac artery is larger and essentially free of stenotic lesions. The occluder device would then be placed in the right iliac limb of the stent graft, just bellow the bifurcation of the original stent graft. Most of the current manufacturers of the stent graft devices provide a product for this type of procedure. When this device is not available from the manufacturer of the original device it is also possible to use another company’s product with satisfactory results.

Since the initial endovascular exclusion of an infrarenal AAA by Dr. Juan Parodi in 1990, the technique of using stent-graft prosthesis to treat AAA has evolved rapidly. This case illustrates that this technology is still in its infancy and significant improvements in stent-graft design and delivery systems are necessary to offer the patients with AAA satisfactory and predictable long-term results.

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Opinion for Juan C. Parodi MD
Jefe del Departamento de Angiología y Terapéuticas de las Enfermedades Vasculares.
Vicepresidente del Instituto Cardiovascular de Buenos Aires

On reviewing the case of a 60 year old male who received an endoprosthesis in September of 1998 to treat a AAA, we learned that he had an occlusion of the right limb of the prosthesis 4 days after the initial procedure. And he was treated with Fogarty embolectomy and PTA with a self expandable Nitinol stent at the external iliac artery. The Doppler scan in at the 6 month follow up detected an exaggerated expansive movement of the main body of the prosthesis which was caused by the disruption of the mesh of the stent.

Observations:

The occlusion of the contralateral limb, I believe was related to:

  1. associated stenosis of the iliac arteries of the ipsilateral side.
  2. The limb was placed in a wrong position since the stump was located in the contralateral side. So the graft had to cross to the other side to reach the stump and eventually kinked.

The disruption of the stent was caused by the Fogarty balloon catheter forcedly introduced into the stump to perform the thrombectomy.

What I would recommend in this case is to insert a tube endograft covering the main segment of the endograft, taking special care on preventing compression of the graft protruding into the main cylinder of the body of the endograft.

If this treatment is ineffective what I would do is to transform the aorto bi iliac into an aorto uni iliac procedure.

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Case Resolution

Dr. Oscar Mendiz

We have thought that this mesh disruptions was due to rupture of prolene knots which allows stent rings connection. We agree with the experts comments about the possibility that the mesh disruption had occurred during Fogarty embolectomy and dilatations to solve right limb sub-acute occlusion.

This late prosthetic related complication was endoluminal successfully solved with a straight Stent-Graft (A Cuff with 26 mm. in diameter and 50 mm. in length) implantation through the previous stent-graft.

Cuff introduction was done by a new femoral cut-down (Figure N°4).

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With this endovascular intervention, stent mesh integrity was restored without any peri-procedural complication and was not necessary late surgical conversion.

Patient is now under clinical follow-up.

[ Send questions, opinions and commentaries to interven-pcvc@pcvc.sminter.com.ar ]

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Bioengineering
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Update
Nov/28/1999


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