A basic recipe for treating complicated aortic dissection
A basic recipe for treating complicated aortic dissection
The patient is an active man in his 60’s with a history of hypertension who had known about a right common iliac artery aneurysm for several years and had come for an opinion. He was asymptomatic of pain. He had a prior splenic artery aneurysm embolization about a decade prior to presentation.. CT scan showed a large eccentric aneurysm arising from a retrograde chronic dissection dilating the right common iliac artery to over 4cm. This is typically iatrogenic, but impossible to know for sure. The left common iliac artery was ectatic to 2cm as was the aorta to 3 cm and all were “wavy.” This sort of tortuosity is the result of remodeling in the axis of flow resulting in lengthening of the artery and is found in those with the substrate for aneurysmal degeneration (footnote). He did not smoke and he could climb stairs without dyspnea or chest pain.
On examination, he was a fit middle aged man with a slight paunch. His abdomen was soft and his peripheral pulses were present and normal. Laboratory results were normal, including creatinine. EKG and echocardiogram were also normal.Treatment options were discussed in detail. The patient was paying for the operation himself and wanted to understand in detail the possible options. These included
1. Open aortobi-iliac bypass with a jump bypass to the right internal iliac artery
2. Open aortobi-iliac bypass with ligation of right internal iliac artery
3. EVAR with right external iliac extension after embolization of right internal iliac artery
4. EVAR with parallel grafts to right external and internal iliac artery (off label)
5. EVAR with iliac branched graft to right internal and external iliac artery (off label)
People are known to react with emotions and to decide typically for near term gain over far term benefits. The offer of an operation involving laparotomy and a possible weeklong hospitalization with all the attendant risks of death, heart attack, stroke, ileus, wound infection, pneumonia, organ failure and so on provides a stark contrast to the appeal of endovascular repair which can be done percutaneously, with local anesthesia, and with a short hospital stay. The lifelong CT scans are in the murky future compared to the present which is sharply in focus. This is why few people save for retirement, why profligate grasshoppers far outnumber industrious ants. In the same vein, the offer of an “advanced minimally invasive” solution plays to several cognitive biases that exists in the mind of not only the patient but the health-care provider. These include this preference for short term gain over long term gain, but also viewing all innovation as being necessarily better than what was available.
After going over the operation in great detail, the patient cut me off when I mentioned the need for lifelong followup CT scanning. Because he lives in several countries, typically, he has to pay for his healthcare out of pocket and he balked at the notion of paying for an annual CT scan. He was also disdainful of the possibility of reintervention (quoted at 10%) and having to pay for it. Also, the stent grafts, which he would have to pay for, end up being as costly as a new luxury sedan based on local pricing.
We chose open surgical repair via a midline laparotomy. An aortobi-iliac bypass was performed from proximal aorta to right internal iliac artery and left common iliac artery bifurcation with a jump bypass from the right graft branch to the right external iliac artery. Technically, this sequence was chosen for ease of access to the internal iliac artery with the external clear of graft. Operative time was 3 hours. He was in the ICU for one night. He went home after 10 days after contracting a UTI. In followup three weeks after discharge, because he had fevers, a CT scan was performed (figure). He was treated for an upper respiratory infection which cleared, and he has been doing well since. We are both happy that he will never need a followup CT scan.
The literature supports this stance. The long term followup of the EVAR-1 Trial (Reference 1) is an example. This was the late followup of the prospective randomized study looking at open surgery versus EVAR in 1252 patients. The initial EVAR 1 findings are well known and put into question the long term benefits of EVAR as the initial mortality benefit of EVAR is lost within a few years of treatment. At a mean of 12.7 years of followup, there were more deaths from aortic aneurysm rupture and aneurysm related death in the EVAR group compared OPEN surgery (adjusted HR 5.82, p=.0064), with 13 AAA ruptures. I have mentioned before that the failure of a handful of pacemakers drove the Guidant company to recall over 20,000 of their devices. Plus, the cost of annual CT scans in the treatment group and cost of devices and cost of reintervention have driven the UK’s NICE Guidelines recommending against EVAR in elective AAA repair. The meta-analysis of EVAR-1, DREAM, OVER, and ACE trials comprising 2783 patients is confirmatory, that aneurysm related mortality was significantly higher after the initial mortality benefit of EVAR fades away, and that patients of marginal fitness gain no advantage from EVAR, particularly those with heart or renal disease, and those with PAD had lower mortality in the period of 6 months to 4 years (reference 2).
I post this case, because despite a complications, in this case UTI and URI, the patient did fine. So why is open aortic surgery considered a dying art? Why is there such pushback against the UK NICE Guidelines?During my residency in the 1990’s, in the heyday of open surgery, I observed a lot of mediocre vascular surgeons and a very few great ones. The average vascular surgeon would take 6-8 hours to perform open aortic surgery, and the patient would come out with a typical picture of oliguria, third spacing, SIRS, that would generate a 1-2 week stay that would even be described as the normal and expected course for AAA repair in surgical and critical care textbooks. The best surgeons back in the day did these operations under 3 hours with 100mL blood loss and the patients would spend a day in the ICU (often not needing it), and 3-7 days in the hospital, but they were the exception.A higher percentage of surgeons today can do EVAR well than surgeons 25 years ago could perform competent open aortic surgery. Most surgeons graduating from training rarely see or do open aortic surgery compared to the multitude of interventions. Capable open surgery basically is not available outside of a few centers, and most surgeons admit to not having equipoise to start a new trial with modern devices. Open aortic surgery is a lost art, like growing your own vegetables, dressing your own game, reading cursive script, and dialing a rotary telephone.
It is not for a lack of desire. I have several younger colleagues I have met or interacted with via social media who have an intense interest in gaining open vascular skills. They have organized open skills courses at major European vascular meetings, but I believe that is not enough.The need for exovascular fellowship, the running topic of conversation of older surgeons through the 2000’s, is never as critical as it is now as we see milennia of surgeon-years of experience retiring to golf courses and cottages. The recommendation for preferring open surgery in the younger and fitter patients is sadly out of reach for most patients and surgeons. The same passion in disseminating endovascular knowledge needs to be applied to repair the damage to vascular education by over-relying on and over-prescribing endovascular approaches.
Finally, and sadly, this patient is the exception. When given clear options and outcomes and costs, this patient made a rational decision, choosing value over convenience.
1. Lancet 2016;388: 2366-2374.
2. BJS 2017;104:166-178
Pearls for finding AAA:
1. Tortuosity of the internal carotid arteries including loops and hairpin turns found in patients particularly smokers implies the present of a AAA until proved otherwise
2. Palpating bounding popliteal or pedal pulses in an older smoker implies the presence of a AAA until proved otherwise. Especially if the medical student can feel these pulses.
3. African-American Females with Diabetes almost never get AAA.
4. Palpate their abdomen
This was presented at Dia De La Patología Aortíca Marbella organized by Dr. Fernando Gallardo.
Here is the link.
I recently had to remove a stent graft for infection and got to thinking about how the number of people who could comfortably and confidently manage that has thinned out in the world through the unintended consequence of the medical device market place. In every surgical specialty over the past twenty years, many open procedures were replaced with a minimally invasive option which generally involved adoption of new technology and large costs to the hospital. These newer procedures were touted as easier on the patient while being easier to perform for the average physician than the open procedure that they were replacing. That was the other selling point -that one could do several of these operations in the time it took one open procedure. In most cases, they were at best almost as good as the open procedure but at higher cost.
In the marketplace, minimally invasive always wins. In many specialties it became untenable to practice without marketing these “advanced minimally invasive” skills. Hence, the wide adoption of robotics in urology outside major academic centers -during those years of rapid adoption the surgeons would get flown to a course, work on an animal model, then for their first case a proctor would be flown out and voila -a minimally invasive specialist is born. The problem comes when learning these skills displaces the learning of traditional open surgical skills. In general surgery, it is not uncommon to hear of residents graduating without having ever having done an open cholecystectomy. It is also the case that many vascular trainees graduate with but a few if any open aortic cases. What happens when minimally invasive options run out? Who will do my carotid endarterectomy or open AAA repair?
The first case is an elderly man with an enlarging AAA sac despite having had EVAR about seven years prior. No endoleak was demonstrated but the proximal seal was short on CT. Also, it was a first generation graft which is prone to “peek a boo” endoleaks from graft junctions and stent anchoring sutures. On that last point, I use the analogy of a patio umbrella -after seven seasons, they can leak where cloth is sewn to the metal struts. It is very hard to demonstrate leak of this kind on CTA or duplex ultrasound because they are small. The patient had his EVAR because he was considered high risk for open repair at the time of his operation -moderate COPD, mild cardiac dysfunction. His sac had enlarged to over 6cm in a short time, and therefore open conversion was undertaken. No clinical signs of infection were present. A retroperitoneal approach was undertaken. After clamps were positioned, the sac was opened.
The picture does not show it, but a leak from the posterior proximal seal zone was seen with clamp off. The clamp was reapplied and the graft transected flush to the aortic neck. A bifurcated graft was sewn to this neck incorporating the main body stent graft and aortic neck in a generous running suture. The left iliac limb came out well and the new graft limb sewn to the iliac orifice, the right iliac limb was harder to clamp and therefore I clamped the stent graft and sewed the open graft to the stent graft.
The patient recovered well and went home within the week. He was relieved at no longer needing annual CT scans.
Who needs annual CT scans? Patients with metastatic cancer in remission.
The second patient was an older man referred for enlarging AAA sac without visible endoleak. The aneurysm had grown over 7cm and was causing discomfort with bending forward. He too had been deemed high risk for open repair prior to his EVAR. If he had had an early generation Excluder graft, the possibility of ultrafiltration would be more likely and relining the graft would be reasonable (link). This was again a cloth and metal stent graft which can develop intermittent bleeding from graft to stent sutures, and I don’t think relining will help.
The patient was taken for open repair (above), and on opening the AAA sac, bleeding could be seen coming from the flow divider. It stopped with pressure, but I replaced the graft in a limited fashion from the neck to the iliac limbs as in the first case. This patient did very well and was discharged home under a week.
The third patient was another fellow referred from outside who had an EVAR for a very short and angulated neck, and a secondary procedure with an aortic extension in an attempt to seal the leak had been done. This failed to seal the type Ia leak. This patient too was deemed too high risk for open surgery of what was basically a juxtarenal AAA with very tortuous anatomy.
The patient was taken for open repair, and the stent grafts slid out easily (below).
A tube graft was sewn to the short aortic neck and distally anastomosed to the main body of the stent graft -with pledgets because of the thin PTFE graft material in this particular graft. This patient did well and went home within a week.
All three cases are patients who were deemed originally too high risk for open repair, who underwent EVAR, then underwent explantation of their failing stent graft. Only one involved a patient whose graft was placed off the IFU (short angled neck), but the rationale was that he was too high risk.
What is high risk? In non-ruptured, non-infected explantation of failing stent graft, the mortality is 3% (ref 2) from an earlier series from Cleveland Clinic. With stent graft infection, the 30-day mortality of surgical management from a multi-institutional series was 11% (ref 3) when there was no rupture. From a Mayo Clinic series, stent graft resection for infection came with a 4% 30-day mortality (ref 4). These were nominally all high risk patients at the time of the original EVAR.
Real world risk is a range at the intersection of patient risk and the expertise of the operating room, critical care, and hospital floor teams. The constant factor is the surgeon.
Endografts for AAA disease (EVAR, endovascular aortic aneurysm repair), makes simple work of a traditionally complex operation, the open aortic aneurysm repair. The issue has been the cost and risks of long term followup as well as endograft failure and aneurysm rupture. The Instructions For Use on these devices recommend a preop, a followup 1 month, 6 month, and 12 month CTA (with contrast) and annual followup with CTA for life. These devices were meant to treat high risk patients but high risk patients with limited life spans do not benefit from EVAR (ref 1, EVAR-2 Trial). These have lead the NHS in the UK to propose that EVAR has no role in the elective repair of abdominal aortic aneurysms in their draft proposal for the NICE guidelines for management of AAA (link). While this is a critical discussion, it is a discussion that is coming at least ten years too late. A generation of surgeons have been brought up with endovascular repair, and to suddenly announce that they must become DeBakey’s, Wiley’s, Imperato’s, and Rutherford’s is wishful thinking at best or wilful rationing of services at worst.
In 2006, Guidant pacemakers were recalled because of a 1000 cases of possible capacitor failure out of 28,000 implants for a failure rate of 3.7% -there were 2 deaths for a fatality rate of 0.00007%. EVAR-1 Trial’s 8 year result (ref 5) reported 16 aneurysm related deaths out of 339 patients (1.3%) in the EVAR group compared to 3 aneurysm related deaths out of 333 patients (0.2%) in the OPEN group.
Academic medical centers, behemoths though they are, serve a critical function in that they are critical repositories of human capital. The elders of vascular surgery, that first and second generation of surgeons who trained and received board certification, are still there and serving a vital role in preserving open aortic surgery. My generation -the ones who trained in both open and endovascular, are still here, but market forces have pushed many of my colleagues into becoming pure endovascularists. The younger generation recognizes this and last year, I sat in on an open surgical technique course at the ESVS meeting in Lyons organized by Dr. Fernando Gallardo and colleagues. It was fully attended and wonderfully proctored by master surgeons. This is of critical importance and not a trivial matter. As in the 2000’s when endovascular training was offered as a postgraduate fellowship in centers of excellence, there is no doubt in my mind that today, exovascular fellowships need to be considered and planned and that current training must reinvigorate and reincorporate their open surgical components.
Leriche Syndrome -one of those disease names that adds to our work in a way that an ICD codes and even the “aortoiliac occlusive disease” fails to describe. When I hear someone described as having Leriche Syndrome, I think about a sad, chain smoking man, unmanned, complaining of legs that cramp up at fifty feet, pulseless.
The CT scan will occasionally show an aorta ringed by calcium in the usual places that are targetrs for clamping below and above the level of the renal arteries. Even without the circumferential calcium, a bulky posterior plaque presages the inability to safely clamp the aorta. Woe to the surgeon who blithely clamps a calcified lesion and finds that the rocky fragments have broken the aorta underneath the clamp! The first way to deal with this is to look for ways not to clamp the aorta, by planning an endovascular procedure, but circumstances may necessitate the need to control the aorta despite the unclampability.
The traditional methods of avoiding clamping the calcifed peri-renal aorta are extra-anatomic bypasses including femorofemoral bypass and axillo-femoral bypass. I propose these following options for the consideration when the patient needs a more durable solution while avoiding a heavily diseased aorta.
Not Clamping I:
EndoABF does work to avoid clamping -these are common femoral endarterectomies supplemented by stenting of the aortoiliac segment, including in those with appropriate anatomy, a bifurcated aortic stent graft. This is often not possible to treat both sides, but one side is usually more accessible. Often, people will compromise and perform an AUI-FEM-FEM, but I have found the fem-fem bypass to be the weak link, as you are drawing flow for the lower half of the body through a diseased external iliac artery. The orientation of the proximal anastomosis is unfavorable and in the instance of highly laminar or organized flow, the bypass is vulnerable to competitive flow on the target leg, leading to thrombosis.
The femorofemoral bypass is the option of patients whose options have largely run out. It is made worse when fed by an axillofemoral bypass. Sometimes, you have no choice, but in the more elective circumstance, you do.
Not Clamping II:
The second method is performing a aorto-uni-iliac stent graft into a conduit sewn end to end to the common iliac aftery, oversewing the distal iliac bifurcation.
The conduit is 12mm in diameter, the key is to deliver the stent graft across the anastomosis, sealing it. The conduit is then sewn to the side of a fem-fem bypass in the pelvis, maintaining antegrade flow to both legs. The other option is to sew the conduit to a 14×7 bifurcated graft. Illustrated above is this 12mm conduit sewn end to end to the diseased common iliac artery with wire access into the aorta and a aorto-uni-iliac device. Typically, a small AUI converter (Cook, Medtronic) can be used, but the aorta is often too small even for a 24mm device, and an iliac limb with a generous sized docking segment (Gore) ending in a 12mm diameter fits nicely. Below is a CTA from such a case, where the stent graft is deployed across the anastomosis, sealing it off from anastomotic leaks (exoleaks).
Not Clamping III:
Often, the infrarenal aorta is soft anteriorly and affected only by posterior plaque at the level of the renal arteries. While a clamp is still not entirely safe (I prefer clamping transversely in the same orientation as the plaque with a DeBakey sidewinder clamp), a balloon is possible. I do this by nicking the aorta -simple application of a finger is sufficient to stop the bleeding if you have ever poked the ascending aorta to place cardioplegia line.
A Foley catheter is inserted and inflated. The Foley’s are more durable and resist puncture better than a large Fogarty. This is usually sufficient for control, although supraceliac control prior to doing this step is advised. The aorta can be endarterectomized and sewn to the graft quite easily with this non-clamp.
This has worked well, Although pictured above with an end-to end anastomosis planned, it works just as well end-to-side. I actually prefer end to side whenever possible because it preserves the occluded native vessels for future intervention in line.
The Non-Thoraco-Bi-Femoral Bypass
The typical board answer for the non-clampable aorta is taking the inflow from the thoracic aorta or from the axillary artery -neither of which are good options. The first because the patient is positioned in right lateral decubitus and tunneling is not trivial. The second because of long term durability. The supraceliac aorta, technically it is the thoracic aorta, is often spared from severe plaque and clampable. Retropancreatic tunelling is straightforward, and a 12 or 14mm straight graft can be tunelled in this fashion from the lesser sac to the infrarenal retroperitoneum. It then sewn to the supraceliac aorta and then anastomosed to a 12x6mm or 14x7mm bifurcated aorto-bifemoral bypass, of which limbs are tunneled to the groins.
This worked very well recently, allowing a middle aged patient with severe medical problems, occluded aorta and iliac arteries, with critical limb ischemia, survive with minimal blood loss and home under 5 days. It delivers excellent flow to both legs in an antegrade fashion. Dr. Lew Schwartz gave me a list of references showing that this is not novel, but represents a rediscovery as the papers were published in the 80’s [reference], and buttresses the principle that innovations in open vascular surgery are exceedingly rare, largely because we have been preceeded by smart people.
Conclusion: All of these come about through application of some common sense and surgical principles. The most important this is that the aorta is the best inflow source and reconstructing it with the normal forward flow of down each leg and not reversing directions as in a fem-fem bypass gives each of these options a hemodynamic advantage.
References for Supraceliac Aorta to Lower Extremity Bypass
The patient is an 70 year old man referred for evaluation of claudication that occurred at under a block of walking. He reported no rest pain or tissue loss. He smoked heavily up to a pack a day, with congestive heart failure with an ejection fraction of 40%, prior history of myocardial infarction treated with PTCA, and pacemaker, and moderate dyspnea on exertion.
On examination, patient had a flaccid abdomen through which the AAA could be palpated, and he had no palpable femoral artery pulse bilaterally, nor anything below. He had a cardiac murmur and moderate bilateral edema. Preoperative risk evaluation placed him in the high risk category because of his heart failure, coronary artery disease, and his mild to moderate pulmonary disease.
CTA (pictured above and below) showed a 5.1cm infrarenal AAA with an hourglass shaped neck with moderate atherosclerosis in the neck, an occluded left common iliac artery with external iliac artery reconstitution via internal iliac artery collaterals, and a right external iliac artery occlusion with common femoral artery reconstitution. There was calcified right common femoral artery plaque.
Treatment options included open surgical aortobifemoral bypass with exclusion of the AAA, total endovascular repair with some form of endo-conduit revascularization of the occluded segments of iliac artery, or a hybrid repair.
Open aortic repair in patients with heart failure and moderate COPD can be performed safely (ref 1). Dr. Hollier et al, in the golden age of open repair, reported a 5.7% mortality rate operating on 106 patients with severe category of heart, lung, kidney, or liver disease.
Typically, the hybrid repair involves sewing in a conduit to deliver the main body of a bifurcated or unibody stent graft when endovascular access is not possible. Despite techniques to stay minimally invasive -largely by staying retroperitoneal, this is not a benign procedure (ref 2). Nzara et al reviewed 15,082 patients from the NSQIP database breaking out 1% of patients who had conduit or direct puncture access.
Matched analyses of comorbidities revealed that patients requiring [conduit or direct access] had higher perioperative mortality (6.8% vs. 2.3%, P = 0.008), cardiac (4.8% vs. 1%, P = 0.004), pulmonary (8.8% vs. 3.4%, P = 0.006), and bleeding complications (10.2% vs. 4.6%, P = 0.016).
Despite these risks, I have performed AUI-FEM-FEM with good results with the modification of deploying the terminus of the stent graft across an end to end anastomosis of the conduit graft to the iliac artery (below), resulting in seal and avoiding the problems of bleeding from the usually heavily diseased artery
The iliac limbs of some stent graft systems will have proximal flares and can be used in a telescoping manner to create an aorto-uni-iliac (AUI) configuration in occlusive disease. The Cook RENU converter has a 22mm tall sealing zone designed for deployment inside another stent graft and would conform poorly to this kind of neck as a primary AUI endograft which this was not designed to act as. The Endurant II AUI converter has a suprarenal stent which I preferred to avoid in this patient as the juxtarenal neck likely was aneurysmal and might require future interventions
I chose to perform a right sided common femoral cutdown and from that exposure, perform an iliofemoral remote endarterectomy of the right external iliac to common femoral artery. This in my experience is a well tolerated and highly durable procedure (personal data). Kavanagh et al (ref 3) presented their experience with iliofemoral EndoRE and shared their techniques. This would create the lumenal diameter necessary to pass an 18F sheath to deliver an endograft. I chose the Gore Excluder which would achieve seal in the hourglass shaped neck and allow for future visceral segment intervention if necessary without having a suprarenal stent in the way. I planned on managing the left common iliac artery via a percutaneous recanalization.
The patient’s right common femoral artery was exposed in the usual manner. Wire access across the occluded external iliac artery was achieved from a puncture of the common femoral artery. Remote endarterectomy (EndoRE) was performed over a wire from the common femoral artery to the external iliac artery origin (pictures below).
The 18F sheath went up with minimal resistance, and the EVAR was performed in the usual manner. The left common iliac artery occlusion was managed percutaneously from a left brachial access. The stent graft on the left was terminated above the iliac bifurcation and a self expanding stent was used to extend across the iliac bifurcation which had a persistent stenosis after recanalization.
The patient recovered well and was sent home several days postprocedure. He returned a month later with healed wounds and palpable peripheral pulses. He no longer had claudication and CTA showed the aneurysm sac to have no endoleak (figures below).
I have previously posted on using EndoRE (remote endarterectomy) for both occlusive disease and as an adjunct in EVAR. Iliofemoral EndoRE has excellent patency in the short and midterm, and in my experience has superior patency compared to the femoropopliteal segment where EndoRE is traditionally used. This case illustrates both scenarios. While the common iliac artery occlusions can be expected to have acceptable patencies with percutaneous interventions, the external iliac lesions typically fail when managed percutaneously especially when the stents are extended across the inguinal ligament. The external iliac artery is quite mobile and biologically, in my opinon, behaves much as the popliteal artery and not like the common iliac. Also, the common femoral arterial plaque is contiguous with the external iliac plaque, making in my mind, imperative to clear out all the plaque rather than what can just be seen through a groin exposure.
On microscopy, the external iliac artery is restored to a normal patent artery -I have sent arterial biopsies several months after endarterectomy and the artery felt and sewed like a normal artery and had normal structure on pathology. This implies that the external iliac can be restored to a near normal status and patients that are turned down for living related donor transplantation of kidneys can become excellent recipients. In this case, this hybrid approach effectively treated his claudication but also sealed off his moderate sized AAA while not precluding future visceral segment surgery or intervention with a large suprarenal stent.
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.
The 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.
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.
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.
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.
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.