Complications of Endovascular Stent Graft Repair - HD

Introduction

Hello, my name is Margarita Robson.
I'm a physician who works at Yale University School of Medicine, and today I will talk about complications of endovascular repair of the aortic aneurysms.
I have nothing to disclose.

Objectives

The objectives of this conference is to review anatomy, physiology, and management of the abdominal aortic aneurysms.
Also discuss favorable vascular anatomy for the endovascular aortic repair placement, and describe types of the EVAR prosthesis.
We're also gonna review some options of the EVAR surveillance and describe ultrasound protocol in the valuation of the aorta after the endovascular repair.
Detailed review of complications of endovascular repair will be discussed, and we will also touch base on the management of complications.

Definition of Abdominal Aortic Aneurysm

To begin with, we wanted to talk about what is the abdominal aortic aneurysm?
What is the definition?
Usually when diameter of the dilated aorta is greater than 50% of normal proximal segment is considered to be aneurysmal.
And also, if you have abdominal aortic diameter of greater than three centimeter is considered to be abdominal aortic aneurysm.
This is a very common problem with almost 2.7 millions affected in the United States.
And there is a gender predominance for the males with ratio of six to one, and also it affects an elderly population of greater than 65 years old.
There is association with smoking and the family history is also associated with development of triple A, such as hypercholesterolemia, hypertension, connective tissue disease, atherosclerosis, infection, traumas associated as well.

Symptoms and Types of AAA

Most patients are symptomatic and when they develop symptoms, it may be due to the rupture.
Patients may complain on the presence of acute back pain, hypotension and pulsitile abdominal mass may be seen on physical examination by shape.
AAAs can be divided into the fusiform or true aneurysms, and this is usually to the atherosclerosis and as ular or false aneurysms or pseu aneurysms.
The second type, and this is usually in due to infection or trauma by location.
Abdominal aortic aneurysms can be either supra renal with involvement of the renal arteries and extension of the aneurysm, more proximally, or they could be juxta renal with involvement of the renal arteries and the extension into the more distal portion of the aorta.
Infrarenal abdominal radi aneurysm, those which arise approximately one centimeter below the renal arteries.
So they do not involve renal arteries and the aneurysmal sac will distant distally.
As a tip we can use abdominal aortic aneurysm location.
If the aneurysmal sac is located approximately two centimeter distal from the SMA, it's likely infrarenal aneurysms also may involve not just abdominal aorta, but also can extend to the common IA ies.
And when the common IA IES are measured over 1.5 centimeter, they can be considered an aneurysmal.

Risk of Rupture

There is a high risk of rupture for the AAAs, and the risk depends on the significant growth of the aneurysms and also on the size.
So if the aneurysm is growing over one 0.5 centimeter in six months or greater than one centimeter in 12 months, it is significant.
And when risk of rupture is also dependent on the size of the aneurysm.
So with the size of four to five centimeter, the risk is one to 3%, and it increases significantly when the size of the aneurysm reaches seven centimeter and above.
Also important to mention that all the statistics depends on the gender as the risk of rupture in the females is much higher.
It's approximately four times higher than in men.
Also, the rupture occurs at the smaller size in females and also females have a higher complication rate.
Postviral rate is also much poor in females independent of what kind of repair was utilized open surgery or in the vascular repair.
Therefore, the suggested size criteria for intervention is in females is 4.5 centimeter.

Management of Abdominal Aortic Aneurysm

The management of the abdominal aortic aneurysm is usually either using the open surgery, it's a standard of care or endovascular aortic graft repair.
The indication of surgery the following, if the triple A diameter is greater than 5.5 centimeter or triple a size is greater than a two times, 2.5 times of normal aortic diameter than the surgery is indicated.
Also, if the growth of the aneurysm is fast over one centimeter per year, then the surgery is indicated when patients present with the ruptures, that's automatically goes to the surgery.
And if the patient present with symptoms such as back pain or other abdominal pain symptoms that could be potential warning signs of impeding ruptures.
This is also indication for surgery.
The mortality rate for abdominal aortic aneurysm is very high, of approximately 60% of patients will die after rupture.
When the patients have open repairs or EVAR repairs.
The mortality rate is much smaller.
With the EVAR having a little bit smaller mortality rate relative to the open repair, there's approximately 6% per year long-term EVAR failure.
So now looking at these numbers, we can tell that the death from AA rupture is preventable and the surgical management should be utilized.
Open surgery is a standard of care, as I said before.
However, it's a lengthy surgical procedure that requires a general anesthesia and also substantial recovery time EVARs a little bit better in the way of recovery and also in the way of mortality.
And morbidity is slightly less than the open surgery.
It's less invasive procedure, doesn't require that much of time for recovery.
And also, it's favorable in patients with chronic renal disease and also in patients with COPD and cardiac problems as the there are fewer cardiac events in the perioperative period after EVAR.

Candidates for EVAR

When should we consider and who should be the candidates?
The can is usually the patients who have already predicted surgical mortality of greater than 5%, or if their life expectancy is less than 10 years.
Other comorbidities also can affect the open repair outcome.
And therefore, if there are comorbidities, EVAR is more preferable route of surgery.
Also patients with anatomically suitable triple A favorable for EVAR.
Recent advances in new EVR stands also may include not only intrarenal abdominal aortic aneurysm, but also juxt renal aneurysms.
EVARs can be utilized in both true and false aneurysms and increased complication rates usually can be seen when their iliac arteries are also involved.
And the higher complication rates are seen if the aaas are large in size, and also have less favorable anatomy.
So this is something to consider when choosing the EVAS.

Principles of EVAR

The principles of EVAR is that it's image guided treatment of aa.
Its uses stent graft device, and the prosthesis and device is placed within the native abdominal aorta.
It's usually the axis is through the common femoral artery.
And once it's placed, it's secured proximally and distally to diseased aneurysmal portion of the aorta.
It creates a new conduit for blood flow and eliminates triple sac pressurization.

Types of EVAR Stent Grafts

The types of EVAR stand grafts as following.
So we have either the ones which is suitable for infrarenal EERs, or we can use a fenestrated EVA stents which are juxta renal could be used in juxta renal abdominal aortic aneurysms.
And some of the most common ones that we see is neath and excl excluder, A FX evasion, prime and endur.

Predictors of EVAR Success

Two.
The predictors of EVAR success usually depend on patient vascular anatomy, on neck morphology of the abdominal aortic aneurysm, and also selection of correct and the prosthesis, and it's heavily operated dependent.
So neck morphology, usually we look at a few things in the neck.
So one of which would be the neck length.
The neck length measures usually from the renal artery to the proximal portion of the abdominal aneurysmal sac.
And it's a distance that helps to secure the proximal portion of the EVAR stent.
So if it's 1.5 centimeter or less then it may be not as favorable, but approximately 1.5 centimeter requires full landing zone of the infrarenal fixation.
The angle is drawn between the flow axis of the supra renal aorta and the intrarenal neck and angles greater than 150% are most favorable and angles less than 120% are more difficult just because there is too much of kinking of the neck and therefore it's not gonna provide a good seal and also good placement of the proximal portion of the prosthetic device.
Another factor is the shape and size of the aneurysmal neck.
Usually the best shape is a straight shape of the neck when there is no difference in the diameter between the proximal portion of the neck and the more distal portion of the neck tapered neck is cold when the more proximal portion is dis uh bigger than the distal portion of more than three millimeter in distance.
And therefore, once the prosthesis is placed, it's not gonna be a good seal between the graft and aortic wall.
The reverse tapered morphology of the neck is when the more proximal portion is more narrow and the distal portion of the MUAC is more wide and therefore it's gonna be a possibility of sliding of the stent and a migration of the stent as a complication of this kind of neck morphology.

Imaging Surveillance for EVAR

So there are two major studies imaging modalities that they utilized for imaging surveillance of the EVAR post EVAR procedures.
So it's either a CT angiogram that can be using in also non-contrast cts, and then post contrast cts or Cala Doppler ultrasound.
And both of these modalities are helping to confirm position of the device, assess the integrity of the device, and confirm stability or decrease in size of the aneurysmal sac.
It also helps to evaluate for possible end leaks.

Ultrasound Protocol and Normal Findings

Okay, ultrasound EA protocol and normal findings.
So we are gonna concentrate on ultrasound right now in the evaluation of the EVAR.
So in the beginning we wanted to examine the patient in a with a transducer in a alone axis and then short axis on a gray scale.
And the major thing is that we wanted to evaluate the size of the aneurysmal sac.
It is important to use light pressure technique so that the aneurysmal sac is not gonna be distorted and therefore not gonna be given the arrow in the measurement of the transverse or AP view.
Gray scale not only is utilized for evaluation of gray diameter change but it's also helpful in evaluation of the shape of the aneurysmal sac and also of the graft, and also in the evaluation of integrity of the stand graft and location of the stand In relationship to the proximal portion of the aaa.
A Doppler technique is utilized for evaluation of potency of the stands, and visualization of a flow within the stand helps to exclude occlusions and also absence of INE can help to exclude possible stenosis.
In addition, the c Doppler box should be also positioned within the aneurysmal sac itself, excluding the stent so that we can optimize our assessment of possible flow within the aneurysmal sac.
Outside of the stent, the gain and PFS also should be optimized for possible slow flow that can be detected with outside of the stand.
Retrograde flow also may be seen in adjacent vessels adjacent to the aneurysmal wall, and that that can imply on presence of a feeding vessels.
So evaluation of those is also very important.
Power doppler technique is really helpful when we try to detect the slow flow within the sac or outside of the stent graft.
And specific emphasis should be performed at the edges of the graft and within the aneurysmal sac.

Complications of EVAR

So what are the complications?
The major complications are anoles, approximately 10 to 15% of patients usually develop them within the first three years, and they can result in the delayed rupture of their aneurysmal sac.
Also, other complications, a graft migration.
We will talk about occlusions of the either entire stent or limbs of the stent, and also structural failures of the grafts.
Continued growth of the aneurysm without any abnormalities that can be found with imaging.
Also another complication and graft infections are common as well.
With exceptional specific interest to the development of the EVAR enteric fistulization, ischemia to the either pelvis or to the bowel or to the lower extremity is also common complication and access related injuries in the groin.
Another part of the complications that we'll discuss.

Stent Graft Migration

So first we'll start with the stand graft migration.
This is a complication that was seen by Cleveland researchers, occurring in 3.6% of device mi uh migration was occurring in one year, and causes usually due to inadequate position of the stand graft onto the arterial wall.
It usually occurs at the initial placement or after due to the change in AAA size or shape, and also due to suboptimal preoperative vascular anatomy.
Also can be seen with suboptimal device selection.
So those things needs to be really checked before the surgery starts, such as vascular anatomy and device selection so that we can avoid the stent graft.
Migration management usually is endovascular or open surgical revision.
This is an example of the migrated stent that we see that there is a abdominal aortic aneurysm that is located just inferior to the SMA, so it's a juxta renal aneurysm.
And on the coronal images of the CTA, we could see that the stent is located distal to the aneurysm, so it's migrated coly.
And this is the reformatted images that also shows nicely that aneurysmal sac is excluded from the stents outside of the aneurysmal sac.
And this is a correlative ultrasound images that shows that there is a flow in the SMA and then there is no stent present at the level just inferior to the SMA and stent is seen a little bit more distally to it.

Stent Graft Occlusion

This is an example of a patient who has occluded stand and stand graft.
So as you see on the sagittal views, there is a contrast seen pacifying the normal abdominal aorta, and then at the level of the aneurysm, there is no contrast seen at all, and it's not seen either within the stand lymphs or it's not seen outside either.
So there's this completely occluded Endovascular graft.

Ischemia Complications

Another complication is ischemia and pelvic ischemia is very common.
In general, all ischemic complications comprised of approximately three to 5%.
Pelvic ischemia is usually attributable to distal arta embolization and interruption of hypogastric arterial circulation.
It may be seen if internal IA ies get occluded or stenosis.
And patients usually present with pelvic pain, bleeding, they have a leg and buttock claudication and management usually is a thrombectomy if possible, or a stent graft revision.
Lower extremity ischemia is also very common or known as a trash foot.
It's a well-recognized complication occurring in one to 5% of patients after avar and is commonly associated with limb occlusion and with the distal arta embolization patients present with loss of pulse in the Zales PDs, claudication, rest, pain and cool threatened foot.
So this is an example of a patient who underwent endovascular repair and on the same day, a little bit later on, developed a loss of arterial pulses in the right lower extremity.
So ultrasound was performed that a demonstrated on power doppler absence of flow within the mid portion of the right SFA and also on the spectral doppler.
No flow was detected on the

Colonic Ischemia

Colonic ischemia is another complication related to the embolization and dislodge of atherosclerotic plaques.
The cure is in up to one to 3% of cases after both open repair and EVAR mortality rate is really high up to 50% within one month.
And therefore, recognition of this complication is very important.
And usually the dislodge of mural clot or atherosclerotic debris happens into the SMA and IMA circulation.
Patients may present with a multifocal patchy ischemia in the bowel.
And this is the example of it where we have a patient with endovascular repair and the bowel walls were thickened and the suspicion of a colonic ischemia was entertained.
Patient underwent CT evaluation and if you see there are two days on prior to EVAR, the bowel loops appear normal with a thin walls and perceptible wall.
There is air present within the bowel lumen and on post evar the ct, the uh the colon dis demonstrates a thickening of the wall as well as a fluid filled wall of the bowel.
So this was was a raised concern for ischemia of the bowel.

Limb Occlusion

Another complication that is well recognized as a limb occlusion occurring in up to 5% of patients.
There are two types of limb occlusion.
Early occlusion happens usually in the first two months, and it's due to either hardware kinking of unsupported stand graft limb, or due to extension of a small diameter stand graft into the external ilia ery.
Late occlusion usually happens due to graft migration and dislocation of stent graft components.
It's causes major turbulence of the hemodynamics and eventual thrombosis of the limb.
The treatment usually is thrombectomy or relining of the stent graft with another stent graft.
Anticoagulation therapy also can be utilized or a surgical bypass grafts can be placed.
So this is an example of a patient who had a limb occlusion of the left portion left limb of the endovascular prosthesis.
And if you see on the sagittal view, this is aneurysmal sac that outside of the graft.
And then we have endograft that demonstrate no feeling on c doppler and also on the axial imaging, you can see as well that there is no feeling of the left limb.
The contralateral side is normal, demonstrated normal flow within the right limb.
More distal evaluation of the native common iliac IES demonstrates reconstitution of the vessel with the tardo pars wave forms within.
This is another example of the limb occlusion with correlative in angiogram.
Conventional angiogram demonstrated that there is absolute no flow within the left limb.

Limb Stenosis

Another complication that is related to limb occlusion is limb stenosis, where we can detect a high peak systolic velocities within the lumen of the limb graft.
And this could be related either to kinking of the limb or it could be related to atherosclerotic plaque developing within the limb.
And this is an example of bilateral limb stenosis where both limbs demonstrate s in on a color doppler imaging, as well as very high systolic velocities on a spectral doppler and some bruery artifact on a spectral doppler.
And in the both right and left limbs.

Loss of Device Integrity

Another potential complication is a loss of device integrity occurring in up to 3% of patients.
And this may result in growth of the aneurysmal sac limb thrombosis and rupture.
And this could be due to structural breakdowns such as bending kinking of the stand or fracture of the stand and bulging of the stand graft or graft wear holes formation.
So this is an example of bulging of the stand graft where there's not a uniform graft appearance with some outpouching of the left lateral wall of the graft.
And it's also seen on an angiogram both a CTA and a conventional angiogram, and most likely due to the abnormal appearance of the aneurysmal sac that is irregular.
And triple looped growth of the AAA and rupture is a very serious complication, and usually due to the continuous enlargement of the aneurysmal sac resulting in the rupture.
Ruptures occurs in 1.2% of patients after EVAR procedures and most common cause is presence of anoles.
So we will right now concentrate on end leaks, their types and how to diagnose each one of them.
This is an example of the patient who underwent endovascular graft repair, demonstrated growth of the abdominal aortic aneurysm aneurysmal sac up to 8.3 centimeter, and presented with abdominal pain.
CTA was performed that demonstrated that the aneurysmal sac is very large and there is a the discontinuation of the wall of the aneurysmal sac with extravasation of blood outside of the aneurysm into the retroperitoneum.
So this is a very severe complication.

Endoleaks

So talking about anoles, we'll start with the anole type one.
And type one anoles usually are due to inadequate opposition between the stent graft and artery at either proximal or distal attachment.
Aneurysmal sac is exposed to the aortic pressure and therefore it has a very high risk of rapture.
There is a type one endo leak divided into the one A type that corresponds to proximal portion of the stent graft and type one B that corresponds to the distal portion of stent graft.
There is a third type one C that is due to inadequate seal of iliac occluded device.
And usually when the end leak type one is identified, it has to be repaired.
This is an example of type one a end leak where we see that there is a blood flow seen outside of the endovascular stent.
And we see that there is a flow extending from the proximal end of the stent into the aneurysmal sac.
Spectral doppler obtained at the level of the aneurysmal sac demonstrates puls ity within the aneurysmal sac.
And this is a seen loop that shows how the blood extends from the stand graft into the aneurysmal sac, forming so to say to the aneurysm within part of the aneurysmal sac is thrombose.
And this is correlated CTA that shows extravasation of intravenous contrast into the aneurysmal sac at the posterior aspect of the most proximal portion of the stand and seem better on the sagittal images.
This is an example of type one B and the leak where we see that there is a flow seen outside of the stent graft limb.
And this is the more distal left common IAC artery limb.
And correlative CT images also demonstrates contrast materials the outside of the most distal portion of the stand graft.
And this is a companion case for type one A and the leak where we see again that blood flow is in outside of the graft stand at the proximal portion of the graft.
Endoleak type two is the most common type of endoleak and that occurs in the patients up to 20 to 30% of patients.
It's persists in 10 to 15% of patients after six months and is due to retrograde feeling of aneurysmal sac through the branch vessels.
It's can be divided in the type two A, whereas the retrograde feeling is from the inferior mesentery ery and could be divided in the type two B where the feeling is from the lumbar arteries in 50% of patients and may close spontaneously.
This is an example of a type two a endo leak where we see that there is a blood flow can be detected within aneurysmal sac, and it comes from the anterior lateral left anterior lateral positioning of the aneurysmal sac.
And there is a characteristic to and fro flow seen at the level of the vessel that is adjacent to the aneurysmal sac that is characteristic of a retrograde feeling of aneurysmal sac through this vessel.
And that was IMA and this is a a lone axis view through the graft where we can see that there is a feeling retrograde feeling of the aneurysmal sac through this IMA vessel that is positioned anteriorly And CTA again demonstrates the contrast opacified IMA that is a feeling the aneurysmal sac resulting in a type two a endo leak.
And this is another companion case where we see that there's a IMA is filled with color onco doppler and flow is seen in the aneurysmal sac.
This is an example of a type two B and the leak through the lumbar artery.
As you can see that the vessel, the feeding vessel is located posterior to the aneurysmal sac, again at the edge of the aneurysmal sac.
Therefore, it's really important to scrutinize the entire diameter of the aneurysmal sac looking for those aneurysms.
Once you find one, you wanted to put your spectral doppler so that you can assess the two and fro flow for two andro flow within this vessel.
That would be a characteristic for the feeding vessel.
And this is the patient, the same patient who underwent embolization of the feeding vessels.
So this is the coils within the the fill in the vessel.
And we have also pre-image where we can see how this vessels lumber vessels is feeding the aneurysmal sac.
So the next type of end leaks is type three, which occurs due to either tear in the body of the graft or inadequate opposition of the graft and the wall of the aneurysm, or is due to the separation of the endograft components.
Again, there is gonna be a exposure of the aneurysmal sac to the arterial pressure, which will cause expansion of the aneurysmal sac.
And possible rupture and treatment usually is realigning realign the stent graft with a new stent graft component.
So this is an example of the type three endo leak, where on Sagal view we see that there is disruption of the wall of the graft.
And again, on the trans transverse view view, again, we see that there is a small disruption of the wall of the graft.
And if we place the spectral doppler outside of the stand graft, we can detect that there is a arterial wave forms can be found.
And this is the Athena loops in the transverse plane, which demonstrate that there is a a separation of the wall at this level with a blood extending into the aneurysmal sac.
Type four andic usually is caused by too many pores in the graft and it secures intraprocedurally and it's rare and usually resolves after the anticoagulation therapy is discontinued.
Newer devices no longer have this issue, so we have multiple pores within the graft and they all leaking outside into the aneurysmal sac.
This is an example of a type four and the leak where we see that there is a multiple areas where the blood flow is extending from the stands into the aneurysmal sac.
We have two and fro flow within this vessels and the vessels happen at multiple levels and also anteriorly and posteriorly in the same patient.
So this is one of the Cena loops, which shows that there is a extent of blood flow outside of the stand the more lateral and inferior aspect of this graft.
And this is an example where it's more posteriorly.
There is extension of blood flow.
This is more anteriorly extension, so it was at least three or four areas of graft leaking were found.
And that's a correlative images, again, more laterally and more lateral posteriorly and more anteriorly extravasation of contrast from different aspects of the of the graft itself.
Type five is the last type of anoles that we will discuss today, and it's usually there is no demonstratable cause to it, and it's also known as an end detention.
It's a diagnosis of exclusion usually.
So we don't usually find any findings associated with it.

Graft Infection

The next complication that I wanted to discuss is infection.
Again, this is a rare complication.
However, even at our institution in the last few years, we saw a lot of patients with infected graft stands.
So the incidence is in the literature is up to 1%.
And if it's not treated appropriately, then it can result in generalized sepsis and death.
There are three major mechanism that can cause the infection of the graft.
One of them is the contamination of the graft during the placement.
Another one is infection from another remote source such as like appendicitis or infected renal stone or bowel diverticulitis.
So somewhere remotely the patient develops an infection and that can spread to the stand graft.
And the last one is development of the aorta enteric fistula management of this complications usually removal of the entire graft, treatment with antibiotics and then if necessary, placement of another graft.

Aortoenteric Fistula

So aorta enteric fistula is a really serious complication and with a high mortality rate, and it's due to communication of the aorta.
After EVAR treatment with adjacent bowel, there is a reflux of air from bowel can be seen into the vascular lumen.
And this can be detected either on a CT or ultrasound.
And patients may present with blood loss, bloody stools, abdominal pain, sepsis, or hypertension.
The management usually surgical or endovascular intervention.
This is an example of it where on sagittal view we see that there is a graft and there is a persistent attachment of the bowel to the aneurysmal sac.
Unfortunately, on this image, we were unable to detect echogenic foresight within the aneurysmal sac or on a spectral doppler.
Sometimes you may find the characteristic peaks that are related to the air that is identified on a spectral doppler.
And this was not present on this examination.
Correlative CT images in the axial plane demonstrate large amount of ear within the aneurysmal sac and adjacent bowel loops that close in approximation to the aneurysmal sac, likely resulting in our enteric fistula.

Other Complications

Other things that we can see as a complication of the posterior procedures is a formation of aneurysm just distal to the graft.
And such as in this patient.
Prior to the EVR that I don't have an image of it, there was no evidence of common iliac artery aneurysm.
And after var placement, a few months later, the patient developed a 2.5 centimeter aneurysm of the right common iliac artery, and it can be seen right in this area.
And this is due to sometimes turbulence flow at the distal portion of the stand graft and which will result in a formation of aneurysm at this level.
And this is a last example that I wanted to discuss is the axis arterial injury, whereas the injury actually happens at the entry side while the placement of the endovascular stand graft is happens usually the period it occurs in up to 3% of EVAR procedures and it may include arterial thrombosis of the vessel that is utilized for entry point, also RTL dissection or pseudo aneurysm formation.
And most of the times this is due to the large size of the catheters that needs to be advanced into the common femoral arteries for placement of the stand grafts.
And this is an example of the i pseudo aneurysm in the groin after placement of the evar.
And we can see that there is a characteristic to and fro flow seen within the neck of the pseudo aneurysm.
And this is a y sign on color dola within the aneurysmal sac in the groin.

Summary

As a summary, I wanted to say that EVAR is an effective, minimally invasive procedure that has revolutionized AAA repairs, making interventional safer in high surgical risk patients knowledge of the individual's cul anatomy, appropriate follow-up technique and prompt recognition of potential complication is essential for accuracy and interpretation of pre post-procedural imaging studies to ensure success of EVAR and ultrasound CTA complementary imaging modalities that play a great role in surveillance of the EVRR patients and assessment of EVR complications with ultrasound offering a non-invasive means for quick evaluation for potential complications.
This is a list of references and thank you.