The Geometry of Parallel Grafts in the Iliac Arteries

The development of metachronous common iliac artery aneurysm, or progression of them, after prior treatment with EVAR (endovascular aneurysm repair), particularly with “bell bottoming” is typically treated with coil embolization of the internal iliac artery and extension of the stent graft into the external iliac artery. While CH-EVAR has been in the news with the recent results from the PERICLES registry, I have never been entirely convinced of its durability. That is different in the case of building parallel grafts in an iliac limb of an EVAR graft (reference).

Here, the geometries, thrombosis, and forces combine to make gutter flow and endoleak unlikely. Choosing the right size of stent grafts to channel to the external and internal iliacs seems to be a challenge, but is easily solved by this scheme -which I can’t claim as my own, but was thought up by a surgeon in upstate New York who choses to remain anonymous.*

The diameter of the stent graft to be sealed to is measured and an area calculated. The sum of the areas of the two grafts to be placed need to equal or slightly exceed the area of this inflow stent graft. If you have decided the size of the external iliac graft, for example, then the diameter of other graft is merely a few geometric formulas away.

Here is a table that can be helpful in avoiding those formulas.
diameter area table.jpegThe inflow graft area is taken from its measured diameter. Then usually one or the other artery has an obligate size -a size the graft has to be while the other has more “wiggle room.” The other thing that comes from experience is that the AFX graft’s iliac limb extension don’t get the B-infolding that can affect an oversized stent graft placed in a small artery and it accomodates a neighbor well.measurement_3

For example, take this patient who after EVAR of aortic aneurysm with AFX developed metachronous dilatation of the common iliac artery to 3.9cm with abdominal pain. The average diameter is 18.5mm. From the table, that rounds to 19mm corresponding to 283.53 square mm. If the internal iliac artery requires a 13mm graft, that is 132.73 square mm, the difference being 150.80 square mm. That corresponds to a 14mm diameter graft, but a slightly larger graft is preferred for oversizing. The external iliac artery is 8mm, and putting a 13mm Viabahn (largest available) in that would result in the B-infolding in the 8mm external iliac. Here, I bailed myself out by simply placing a 20mm AFX iliac limb extension, which by virtue of its design is resistent to infolding and tolerant of parallel grafts laid alongside in constricted channels. I found that the AFX iliac limb, a 20-13mm x 88mm length extension well suited for this.

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The AFX graft limb seems to adapt to the presence of the parallel “sandwich” graft which is deployed second and ballooned last. In followup, there was shrinkage of the common iliac artery aneurysm sac and no endoleak.

postop_1

postop_2.jpg

Compared to my other parallel graft case treating a metachronous saccular common iliac aneurysm years after an EVAR with a Gore endograft (link), which by table calculation, resulted in 8% oversize in calculated areas, this particular technique with a large AFX graft and an appropriately sized Viabahn seemed to work well the setting of a previously placed AFX graft. It allows one to avoid hypogastric occlusion.

The final option of a femoral or external iliac to internal iliac bypass after extension across the bifurcation to the external iliac artery is still a reasonable choice, although it seems to be receding into history.

Reference

Smith, Mitchell T. et al. “Preservation of Internal Iliac Arterial Flow during Endovascular Aortic Aneurysm Repair Using the ‘Sandwich’ Technique.” Seminars in Interventional Radiology 30.1 (2013): 82–86. PMC. Web. 9 Dec. 2016.

*While these grafts are not FDA approved for use in this manner, many times, with a prior endograft or graft in place, using the currently available and approved Gore Iliac Branch Endoprosthesis (IBE) in this common scenario would still be off label usage of an approved device, and only if it is feasible, which most times is not. For nonmedical readers, many commonly available devices and medications are used off-label, such as aspirin for blood thinning.

External iliac remote endarterectomy restores the artery to normal, opening the way for EVAR, TAVR, TEVAR, and transplant: alternate applications of EndoRE

preop-cta

One of the nice things  about practicing at the Clinic is being able to offer unique solutions. A severely diseased or occluded external iliac artery (EIA) can be a vexing problem, particularly if bilateral, in this endovascular era. Many cardiovascular devices require femoral access that has to traverse compromised iliac arteries -those with large (>16F) delivery systems require a sufficiently wide path to get the devices to the heart and aorta. Also, living related donor kidney transplantation is predicated on minimizing risk to maximize results and having significant iliac plaque negates one as a recipient for this high stakes elective procedure. In situations where the EIA is too small to accommodate devices because of atherosclerotic plaque, the typical solution is placement of a conduit to the common iliac artery or the aorta. The practice of “endopaving” with a covered stent graft and ballooning is also described, but its long term outcomes are not reported and the internal iliac artery is usually sacrificed in this maneuver.

This patient presents with lifestyle limiting claudication and an absent right femoral pulse. ABI is moderately reduced on the right to 0.57, and he had no rest pain. CTA at our clinic revealed an occluded EIA bracketed by severely calcified and nearly occlusive plaque of the common iliac artery (CIA) and common femoral artery (CFA).

cta-preop_7
Centerline Projection

The patient was amenable to operation. Traditionally, this would have been treated with some form of bypass -aortofemoral or femorofemoral with a common femoral endarterectomy. While endovascular therapy of the occluded segment is available, one should not expect the patencies to be any better than that of occlusive lesions (CTO’s) in other arteries. Hybrid open/endovascular therapy is an option as well with CFA endarterecotmy and crossing CIA to EIA stents, but I have a better solution.

The common femoral endarterectomy rarely ends at the inguinal ligament, and is uniquely suitable for remote endarterectomy, a procedure from the early to mid twentieth century.

endoRE graphic
Steps in Remote Endarterectomy

 

The addition of modern fluoroscopic imaging and combining with endovascular techniques makes this a safe and durable operation.

pre intervention.png

The patient was operated on in a hybrid endovascular OR suite. A right groin incision was made to expose the common femoral artery for endarterectomy and left common femoral access was achieved for angiographic access, but also to place a wire across the occlusion into the common femoral artery.

All actions on the external iliac artery plaque are done with an up-and-over wire, allowing for swift action in the instance that arterial perforation or rupture occur. This event is exceedingly rare when the operation is well planned. With this kind of access, an occlusive balloon or repairing stent graft can be rapidly delivered.

The common femoral endarterectomy is done from its distal most point and the Vollmer ring is used to mobilize the plaque. A Moll Ring Cutter (LeMaitre Vascular) is then used to cut the plaque.

Ring dissection.png

Cutter.png

The plaque is extracted and re-establishes patency of the EIA.

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Plaque Specimen

The plaque end point is typically treated with a stent -in this  case, the common iliac plaque was also treated.

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What is nice about this approach is that this artery has been restored to nearly its original condition. I have taken biopsies of the artery several months after the procedure in the process of using the artery as inflow for a cross femoral bypass, and the artery clamped and sewed like a normal artery and the pathology returned normal artery.

This has several advantages over conduit creation which can be a morbid and high risk procedure in patients who require minimally invasive approach. A graft is avoided. The artery is over 8mm in diameter where with stenting up to 8mm with an occlusive plaque, the danger of rupture is present, and often ballooning is restricted to 6mm-7mm. This is insufficient for many TEVAR grafts and TAVR valves.

For patients being worked up for living related donor transplants who are turned down because of the presence of aortoiliac plaque, those with the right anatomy can undergo this procedure and potentially become candidates after a period of healing.

 

The Interrupted Natural History of Aortic and Iliac Artery Aneurysms

graphic

The patient, now in his 90’s, found out about his aortic and iliac artery aneurysms in his early 80’s, had been offered repair, but had refused. Several years ago, one of my partners emergently repaired his ruptured AAA (abdominal aortic aneurysm) via a retroperitoneal approach using a tube graft. At the time of the repair of the AAA, the common iliac artery aneurysms (CIAA’s) were not ruptured and would have added risky time to the repair. He survived and had a postop CT done about two years ago which showed his CIAA’s.

CT 5cm L CIAA 2014.png
Two years ago
The patient chose not to pursue repair of these aneurysms, I assume figuring that at his age, he’d again take the chance that he would pass on without the hassle of another procedure.

He was recently admitted for treatment of another condition, when his physicians noted a large visible pulsatile mass on his lower abdomen.

CIAA

A CT scan was performed. It showed a 13 cm left common iliac artery aneurysm which was responsible for the visible puslatile mass and a large right common iliac artery aneurysm. The left internal iliac artery was thrombosed. His right common iliac artery aneurysm was over 5cm in size.

CT 13cm L CIAA preop

My partner, Dr. Ezequiel Parodi, was consulted for this case. He performed a percutaneous EVAR. The procedure was made difficult by tortuosity in iliac artery and the tube graft in the aorta requiring a secondary access from the arm to straighten out and advance the stent graft (aka body floss).

Dr. Ezequiel Parodi
 
In followup, the aneurysms decreased in size and showed no endoleak around a patent stent graft.

CT postop L CIAA (1)

Common iliac artery aneurysms expand at a rate proportional to their starting size and have increased rates of expansion in those with prior aortic aneurysm expansion (ref 1). Rupture probably signals a tendency to expand rapidly. There is evidence that iliac ectasia and aneurysms left over after tube graft repair (aorto-aortic) of AAA is benign and can be safely observed (ref 2), but these were all small at the start.

I had been trained at the dusk of the open surgical era and the dictum was aortobi-iliac bypasses to avoid future problems with the iliac arteries. With EVAR, and soon bifurcated iliac branched stent-grafts (currently on trial), staged repair of metachronous iliac aneurysms after tube graft repair of AAA has not only an appeal, but some logic as open bypass to iliac bifurcations, particularly in large men, is challenging and potentially morbid. This is a case of a patient who had a large iliac aneurysm that was not repaired initially due to the exigencies of ruptured AAA and had refused planned staged repair. His aneurysm grew from over 5cm to 13cm in 2 years time without rupturing. Such good fortune is very rare.

Vascular surgeons like to collect large aneurysm stories like fishermen talk about big fish. This is the largest unruptured common iliac artery aneurysm I have seen. While it is baffling to many who are in healthcare, it is important to understand noncompliance is common. Denial is a powerful urge, and a uniquely human one.

2014-03-25

 

References

  1. J Vasc Surg. 2009 Apr;49(4):881-5
  2. Surgery. 2008 Nov;144(5):822-6.

Never Stop Following Stent Grafts -Type IV endoleak causing slow growth in 12 year old stent graft

Centerline

 

The patient had undergone EVAR for bilateral common iliac artery aneurysm with the original Gore Excluder stent graft a dozen years before with coil embolization and extension to the external iliac on the larger side and femoral to internal iliac artery bypass on the other side. A coagulopathy, one of the clotting factor deficiencies, had made him high risk for bleeding with major open surgery. His aneurysms never shrank but remained stable and without visible endoleak by CT for a long time resulting in ever longer intervals between followup.

2013_1
2013

Between 2009 and 2013, there was subtle enlargement on the embolized side without a type I or type III leak, and the patient was brought back a year and a half later, with further growth of the sac.

1-2015_3
2015

This was a relatively rare type IV endoleak that was causing sac enlargement due to excessive graft porosity of the original Excluder’s graft material. Its treatment is either explantation or relining. We chose to reline the graft with an Excluder aortic cuff at the top and two Excluder iliac limbs.

2015-11-26 13_25_23

This was done percutaneously and in short followup, there has been stabilization and even some reduction in the aneurysm circumference.

CT Scans

 

It was long known that a certain percentage of PTFE grafts “back in the day” would sweat ultrafiltrated plasma. The relative porosity of the grafts allowed for transudation of a protein rich fluid.

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Tanski W, Fillinger M. J Vasc Surg 2007;45(2):243-249.

 

 

 

 

 

 

 

This results in a hygroma formation. I remember seeing this in AV graft fistulae back in the 90’s -after flow was introduced, the grafts would start sweating! The newer grafts are lower porosity and this is seen very infrequently. Drs. Morasch and Makaroun published a paper in 2006 comparing parallel series of patients who received the original Gore Excluder (OGE), the currently available Excluder Low-Permeability Device (ELPD), and the Zenith device (ZEN). Sac enlargement occurred in equal measure between OGE and ZEN but zero was reported for the ELPD.

Slide3
Haider S et al. J Vasc Surg 2006;44(4):694-700.

The ELPD had higher rates of sac shrinkage than the OGE, and equal rates of sac shrinkage compared to ZEN.

Slide4
Haider S et al. J Vasc Surg 2006;44(4):694-700.

The diagnosis in my patient’s case came about through serial followup through a decade. While I doubt that the aneurysm would have ruptured in the same way as in a Type I, II, or III endoleak, I am sure it would have progressed to developing symptoms from aneurysmal distension or local pelvic compression.

Is it possible to visualize this kind of endoleak at the time it is suspected? I came across a case series from the Netherlands using Gadofosveset trisodium which takes longer to clear than the usual Gd-based MR contrasts and they successfully visualized transudative leaks in 3 serial patients with the original Excluder graft.

Slide2
Cornelissen SA et al. J Vasc Surg 2008;47(4):861-864.

The problem is that Gd-based contrasts have toxicity, especially for patients with poor renal function. The protocol is time consuming. And I suspect that ten years out, a lot of grafts will have positive findings, especially cloth based grafts that are sutured to their supporting stents, without clinical basis for treatment as their sacs size are likely stable on a year to year basis.

That said, as we are well into the second decade of commercially available stent grafts, it is even more important than ever to continue lifelong followup even for what is assumed stable, patent grafts and anatomy.

A Matter of Degrees: The Terrible Aortic Neck Solved With Geometry

CTA AAA with pancreatitis_1

The patient, a younger middle aged woman, was referred for treatment of a large, growing infrarenal AAA over 8cm in size complicating a severe pancreatitis. The pancreatitis occurred about a month prior to presentation and resulted in a substantial pancreatic leak. At the time of that presentation, her AAA was found incidentally and was about 7cm. In the interval, her pain resolved and she was asymptomatic. On examination, her abdomen was soft, and a large aortic aneurysm was easily palpable.

Pancreatitis with surrounding retroperitoneal fluid leak
Pancreatitis with surrounding retroperitoneal fluid leak
CT scan was performed showing an enlarging AAA over 8am and abundant retroperitoneal pancreatic fluid without abscess or infection. The AAA was infrarenal but complicated by a severely tortuous, short infrarenal neck with 90 degrees of angulation and about 8mm in length. As the pancreatic leak was yet early in the process, no pseudo aneurysms had formed. MRCP showed no active leak.

Short neck
Short neck

Greater than 90 degree neck angulation
Greater than 90 degree neck angulation
Other than the pancreatitis, the patient, who was in her 50’s, was an otherwise good risk patient.

The treatment options were:
1. Wait until pancreatic fluid resolution or pseudo aneurysm formation, then standard open repair of the large aortoiliac arterial aneurysm. Not desirable because of the relatively rapid aneurysm growth and current size.
2. EVAR -This is outside the IFU for any of the available devices because of the highly tortuous neck anatomy. While note shown, the external iliac arteries were 5mm in diameter, but in the absence of plaque, was possibly due to spasm. The Nellix device is yet on trial, but there are limits on how much you can straighten this neck. The devices with suprarenal stents end up straightening out the graft with deployment of the graft in an ellipse. This also means loss of seal zone length which decreases with oblique deployment. FEVAR is not possible because of this neck tortuosity as well but was considered briefly.
3. Homograft repair or Rifampin soaked graft repair -The former is costly and still susceptible to infection from a virulent organism as is the latter, but both are likely safe with likely foregut flora.
4. Neo-Aorta reconstruction (NAS) with deep femoral vein. This could work, but is time consuming and relatively morbid. The tactic of mobilizing the vein and then repairing the aneurysm in a separate, staged fashion the following day or two is reported to shorten the overall operative time. This patient would require both femoral veins to be harvested.
5. Aneurysm exclusion and extra-anatomic bypass with axillofemoral bypass. Offered to complete this list, this is the least desirable option given the poor long term behavior of axillofemoral bypasses in younger patients.

When faced with this kind of challenge, it makes sense and should be standard practice to get the opinion of the group. I happen to have excellent partners to run this kind of cases. The consensus was this: EVAR with accepting a short term result to temporize until definitive repair could be done. I found this acceptable. I chose to use the Excluder device because it allows for redos of the proximal deployment (C3 Delivery system) and the 23mm and 26mm devices used 16F access. A detailed discussion with the patient and the intention to eventually definitively repair open was discussed and patient was agreeable to proceeding. Plan B’s of Rifampin soaked graft replacement and NAS was also discussed.

I tried two things that was different. I felt that a stiff wire would result in horizontal orientation of the top of the graft, and so I placed a bend in the wire. Prior experience with unintended bends in wires have taught me that passing these wires is largely tolerated as long as it is done through catheters and sheaths. The other thing I did was bend the top of the delivery system -this was done with some care as I did not want to detach the contraining mechanism.

IMG_6493

IMG_6496

neck

The wire and delivery system modification did tilt the top of the graft away from the left side of the aorta. It had the unintended effect of keeping the wall grabbing anchors away from the near wall while constrained.

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It didn’t tilt the graft as much as I would have liked, but the graft deployed in a left to right fashion that allowed for controlled delivery across all of the available neck. Gratifyingly there was seal (below). I flared the right, while excluding the left iliac bifurcation because of the larger iliac aneurysm.

implant angio -46

As this was done percutaneously, the patient recovered rapidly and was discharged a day later. The question philosophically for me is if the seal remains intact, would there ever be a need for explantation? The patient only received perioperative antibiotics, and I felt long term antibiotics was not indicated. Standard followup was arranged.

There is no question there is a need for devices designed for this kind of neck anatomy. These devices need to bend over to angles at least 90 degrees and unbend based on delivery system design. They need to be low profile as this facilitated repair in this patient with small access vessels.

Parallel Grafts in the iliac bifurcation -an option at least until branched grafts become commercially available

CTA_1

This patient had developed metachronous common iliac artery aneurysms after aorto-bi-iliac graft placement of a AAA a decade ago. This is not infrequent occurence in a significant number of patients with aneurysmal degeneration seen in the thoracic or visceral segment abdominal aorta, iliac arteries, and popliteal arteries, years after a primary AAA repair. The patients are often older than they were at the original repair, with concomitant risk factors, and so a minimally invasive option is preferred.

Right CIAA -vulnerable tissue

saccular r ciaa

The teaching during my fellowship was that aorto-iliac bypasses for aneurysmal disease were to be taken to the iliac bifurcation to go around vulnerable tissues. These tissues vulnerable to aneurysmal degeneration were infrarenal aorta up to the renal artery origins, common iliac and internal iliac arteries, and popliteal arteries. An anastomosis to the iliac bifurcation however normal appearing may degenerate given enough time. This patient developed a saccular aneurysm on the right iliac bifurcation and a small internal iliac artery aneurysm (1.5cm).

CTA_2

This was treated with coil embolization and stent graft from the right iliac limb to the external iliac artery.

RCIAA treatment

This is the standard endovascular therapy for common iliac artery aneurysms, and acceptable in the setting of unilateral disease, and in a staged fashion has been considered acceptable for bilateral disease, acknowledging there is a 10-40% incidence of buttock claudication and when the contralateral hypogastric is occluded or when the patient is diabetic, the risk of buttock or colorectal necrosis is not insignificant. The patient had transiently some buttock claudication and hip and thigh neuralgia with walking but this improved in the weeks leading up to treating his left common iliac artery aneurysm.

Left CIAA

The left common iliac artery bifurcation is sometimes challenging to access from a midline incision and exposure requiring a separate sigmoid mobilization. In men, the narrow pelvis can increase the challenge, so it is without fault that sometimes common iliac artery is left behind. This is what became aneurysmal, developing into a 3.0cm fusiform aneurysm beyond the left limb of the graft.

CTA_6

The internal iliac artery had a moderate 50-75% stenosis at its origin but was not aneurysmal, and I chose to revascularize this. The patient was sexually active and walked for exercise. My options included proceeding with left hypogastric embolization and stent grafting, mirroring the right but with a significant risk for buttock claudication, sexual dysfunction, and a small risk for colorectal ischemia. Other option is an external iliac or common femoral to internal iliac artery bypass which is an excellent option in good risk patients.

Endovascular options

Iliac branched stent grafts are undergoing trial. My center is participating in both available industrial FDA approval trials (disclosure, I am site PI for the Gore trial), but this patient’s presentation and anatomy exclude him from the trials. The final option is placing a parallel stent grafts -one to the internal iliac artery and the other to the external iliac artery from a large common iliac stent graft. While not ideal, until branched grafts become available, this remains a viable option. The principle is to size the grafts to minimize potential gutters between the grafts, and have long seal zones to minimize the impact of the gutters. Access from two points is required to get two grafts into position. With the acute angle of the aortobi-iliac graft, up and over access is generally not possible. The 10mm Viabahn graft that I chose to place in the hypogastric requires a 12Fr sheath, which cannot be placed from the brachial artery, so I prepped for an axillary cutdown. The left common femoral access was percutaneous.

Image-17

The left CFA access allowed placement of a 16mmx10cm Excluder iliac graft limb to cover the aneurysm down to the iliac bifurcation. The left axillary arterial cutdown access allowed placement of a 12Fr sheath (Flexor) to allow access of the left internal iliac artery and safe delivery of a 10mm Viabahn stent graft. The left external iliac artery was sealed with a 13mm Viabahn stent graft that was deployed simultaneously. Ballooning was performed to both.

Completion
Completion

No leak was seen. The axillary access was repaired directly and the CFA access was repaired with two Perclose S devices.

Discussion

Despite initial acceptance of bilateral hypogastric occlusion, even staged, it can be the cause of significant disability aside from buttock claudication, which sometimes does not remit with exercise. Ischemia of the pelvis can drive a plexopathy that can result in motor and sensory neuropathy and disability. Death can occur. Preserving one of the hypogastrics can go a long way to preventing these complications, and everyone eagerly awaits adding iliac branched grafts to the armamentarium.

The Last Vein

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The deep femoral vein offers an important source of autologous conduit, particularly for aortic reconstruction or for limb salvage. It may be mobilized on one day and harvested another in a staged fashion to avoid a prolonged operation. While there is a period of leg edema postoperatively, most tolerate harvest of this vein which may be life saving.