Ultrasound Assessment of the Aorta and post Endovascular Stent Graft Repair - HD

Introduction and Topics

I have nothing to disclose.

And, are we gonna talk today about anatomy and hemodynamics of the abdominal aorta?

I'm gonna describe some ultrasound, pathologists that we see in abdominal aorta, including aa.

And, we'll review some options for AAA repair as well as describe protocols in the evaluation of aorta after endovascular stand graft, repair and surveillance.

And we will review also diagnosis and management of complications of EVAR.

Anatomy and Hemodynamics of the Abdominal Aorta

Aorta is an elastic structure that has a slightly different waveforms in its proximal aorta, where it's a more low resistance waveforms, and more high resistance waveforms.

You can see in mod distal aorta just because it supplies the lower extremities.

Evaluation of the Aorta

And, when we evaluated in aorta, we wanted to, first observe it on the gray scale images.

We wanted to look for any atherosclerotic plaque, dissection, flaps, ulcerations, occlusions, luminal narrowing.

We wanted to measure our aorta in its, longitudinal as well as in transfers view, and look at the proximal, mid and distal portions of the aorta.

And we use in our outer to outer wall measurements.

Pathologies of the Aorta

So, there are multiple pathologies and we're gonna discuss most common ones and one of which, or most dangerous ones.

Aortic Dissection

Aortic dissection is one of those, that is, due to separation of intimal and medial layers of the aortic oil.

And, usually it's an extent of thoracic dissection or could be association.

There is an association with aneurysms and penetrating ulcers, which are origin sometimes for the dissections, causes arthrosclerosis, hypertension, collagen vascular disease, cocaine in New Haven, especially, pregnancy trauma, preexisting conditions.

And it requires urgent care.

That's why we wanted to be able to diagnoses even, when the physicians don't suspect it on a gray scale.

What we are looking for is the dissection flap and its echogenic line.

And on real time imaging, you could see the dissection flap that separates the lumen into the true lumen, which is usually a small in diameter.

And the false lumen that is usually bigger in diameter.

And also if it's patent, it may show you the slow flow within, so you're gonna know exactly what's going on.

And, in some cases you can actually see entry point of the dissection.

With the color doppler, what we are looking for is a potency of the false lumen, as well as patency of the branch vessels in the false lumen.

You can see either two and fro flow, sort of in a diastole.

There is a reversal of flow you may find.

And with spectral doppler, we wanted to see if there is any possibility of stenosis of the true lumen.

And also you wanted to look, what kind of waveforms are there.

In some cases, the dissection flaps will extend into the branch vessels, so it's very important to evaluate those vessels as well.

And in this case, we have a dissection flap in the proximal abdominal aorta.

And, best seen on color doppler imaging and transverse view when part of the, false lumen is actually occluded.

And, when we looked at the kidneys, the right kidney showed no profusion for the exception of a tiny little vessel that was actually supplied by the cortical vessel.

And then on the left side, power doppler showed good perfusion of the left kidney.

So it's really important to look for these things.

And the CTA just confirmed the findings that what they're seen on ultrasound,

Iliac Occlusive Arterial Disease

where the iliac occlusive arterial disease, is most commonly associated with atherosclerosis.

And, it's a chronic progressive disease that leads to complete or near complete occlusion of the aorta and patients in this severe situations, they present with lower, extremity pain, rest claudication, abdominal pain impotence,

and, if it's a full occlusion, usually the distal abdominal aorta will clot until the level of the renal arteries and SMA will become a collateral sort of pathway to supply lower extremities.

Again, we have to evaluate for organ profusion when this kind of things happen.

So on this examination, we look at the, ward on the gray scale, and we see this, large, calcified as well as, mostly a soft tissue plaque that causes luminal narrowing and on color doppler seen as a, aliasing within the vessel and distally in the right SFA as well as left SFA.

We see a TARDIS part with waveforms, representative of a significant stenosis above.

In this, sort of not a happy, patient.

It was a 81 years old female who came with oli uria and groin pain, and she had some right thigh numbness.

And when we evaluated her aorta, we saw that mid and distal portions of the aorta are completely occluded, and the only flow we could see is an proximal aorta.

And we put the spectral doppler and we saw a very low amplitude waveforms.

And, this waveform sort of not really normal just because they hit the obstructive portion.

And, the only vessel that was helping this patient to, preserve the organs and lower extremities was the SSMA.

And you could see it on the CTA that was done two months before, the profusion and the ification of the aorta is normal, and there is lots of other sclerotic disease, but two months later, she really, occluded the entire mid portion and distal portion of the aorta with SMA, serving as a collateral.

So these things can happen really quickly.

So it's important to know that the patient has a significant PID like this one had stent already in a Celia ery and was treated previously.

So, this has to be, very quickly urgently managed.

Takayasu Arteritis

Other things that we can see sometimes in the aorta is, findings of taosa or titis.

It's a dio pathical pulseless disease, and it's, due to granulomatous vasculitis of the large vessels affects aorta, subclavian arteries, carotids.

There is a strong female predominance.

Sometimes we see a higher prevalence in Asian population and patients present with thrombosis stenosis or pseu aneurysm formation within their, vessels.

There is a variable presentation depending on what are the territorial, vessels, affected.

So in this patient on gray scale, you could see that there is a narrowing of the lumen of the ab distal abdominal erta and thickening of the wall.

And that's a characteristic finding the thickening of the wall.

And she's already, she's 27 years old, young female, and her carotid doppler was performed early on and also showed that in a common karate artery, there is a long segment of stenosis with mark thickening of the wall, and elevated systolic velocities, that are consistent with stenosis.

More distally, the common karate artery was, normal and, normal lumen and normal wall thickening or no wall thickening.

Abdominal Aortic Aneurysms (AAA)

Other things that we are always, concerned about is, aaas, and it's a very common, pathology that is seen in up to, 2.5 million of people in the United States.

There are multiple risk factors such as male, and, gender advanced age over 65 years old, history of smoking, history of family history of collagen, vascular diseases, atherosclerosis.

But most of the times patients are asymptomatic, and when they are symptomatic, they may present already either with aortic rupture, and they come in or impeding rupture, and their clinical signs would be, back pain and lower back pain.

So how do we define abdominal aortic aneurysms is when we see that aorta measures over three centimeter, or when the size of the aorta increased in aortic diameter 1.5 times more than, than the normal segment.

We divide abdominal aortic aneurysm into by shape, into fusiform, and that's usually a true aneurysms and usually due to the atherosclerotic disease or due, by, they could be ular.

And this is a false aneurysms and most of the times associated with infectious process or trauma.

Patients with IV drug abuse, they develop mycotic aneurysms, and that's the way that looks by location.

We divide them, aorta into supra renal aneurysms, that involve renal arteries and extends proximally juxta renal that involves a renal arteries and extend distally or intrarenal about 10 millimeter lower than the renal arteries.

But if you follow the rule that if you see that AA is over 20 a two centimeter below the SMA, most likely you're dealing with infrarenal abdominal aneurysm.

Ultrasound is the best modality to evaluate or screen for AAA and do the surveillance for AA with accuracy of a hundred percent.

And screening usually is offered to patients who are, males over 65 years old and who has a history of smoking.

And the whole point of screening is that to reduce mortality from aaa, there are special intervals between ultrasound survivor, surveillance, where developed and it's, dependent on its size.

So annually you would screen somebody or, do the surveillance, who has aneurysm three to four centimeter, every six months if it's four to 4.5 centimeter aneurysms, three to six months, every three to six months if it's an aneurysm of 4.5 to five centimeter.

And then, you're thinking about either screen, again, doing the surveillance or you send the patient for the elective surgery.

Risk of Rupture

Why we wanted to screen is because there is a high risk of rupture of aas, and it it is known that, the risk of rupture depends on growth rate and also the size of the aneurysm.

So what is considered to be the significant growth, when the AA measures greater, I mean, the significant growth is, if it's, growing greater than one, centimeter in 12 months.

And, this is important number to remember.

And also risk of rupture, if, is higher, if the aneurysmal sac is large, for example, five to seven centimeter aneurysms have, up to 11% of risk rupture per year.

Also, statistics depends on the gender, and it's known that females, have a higher risk of rupture, and, they rupture at the smaller size of the aneurysmal sac.

So if a rupture occurs, there is approximately 60% mortality rate following the rupture.

And this is one of the images that describes or shows, abdominal aortic riss with a complex fluid, envelope in anterior abdominal aorta.

And this is a hemorrhage from, the rupture.

And this is already postoperative, CT that demonstrates the same retroperitoneal hemorrhage associated with the rupture aneurysm.

Management of AAA

There are a few things that you can use for management, either open surgery or endovascular stand graft repair.

The candidates are those who have a diameter of the abdominal order over 5.5 centimeter, or there is increase in size by 2.5 times of normal aortic, diameter.

So if the abdominal aorta, aortic aneurysm would grow, greater than one centimeter, this is also a candidate for, if, for treatment.

And of course, those who present already with, ruptured and symptomatic aneurysms.

Multiple studies were done that confirmed that EVAR has a mortality and morbidity lower than, the open surgery, especially those patients who have chronic renal disease or those who have A-C-O-P-D.

And there is a fewer cardiac events in the perioperative patients in this population.

Endovascular Aneurysm Repair (EVAR)

So, EVARs, the stand grafts, I just wanted to show you different types of the grafts, and what it does is that it excludes the aneurysmal sac, from the other, the system, the arterial system.

Predictors of EVAR Success

What are the predictors of EVA R'S success?

You want it to have a really good anatomy and vascular anatomy is number one thing.

So we are looking for neck anatomy, so it has to be a, a good long neck so that the stand graft can be placed, with, no issues and it shouldn't be two torches.

They were the has to have a special angle, angle in the neck and also the neck, shouldn't be flaring, at the top.

So, otherwise it's going to have a high tendency of development of, end leaks.

And if it's, fennels, downward, then it's really gonna, may cause migration of the stent after placement.

So other things, we wanted to make sure that, it's really, good prosthesis is chosen, by the size and, it's heavily operated dependent.

Surveillance After EVAR

There are a few things that we use, for surveillance, either CTA or a color Doppler.

And what we wanted to do is to confirm the position of the device, also assess integrity of the device, and confirm the stability of the size of the aneurysmal sac.

What we wanted to do is we wanted to exclude the and the leaks and there is usually, annual follow up and, or every six months follow up that is suggested.

When we do an ultrasound for surveillance, we wanted to evaluate on a gray scale.

First, we are looking for, position, location of the stent and we are looking for device integrity as well as we measure the aneurysmal sac on the color Doppler doppler.

We are looking for the patency of the stent itself of the limbs, and we're looking for any possible flow within aneurysmal sac that will give us an idea that maybe there is anole.

So specific emphasis usually is made to the edges of the graft and within the aneurysmal sac,

Complications of EVAR

multiple complications associated with EVAR, majority of them are anoles and that's why we spend a lot of time on learning them.

But there is also graft migration.

There is partial complete lip inclusion, structural failures that can happen to it, pelvic or lower extremity or colonic ischemia due to other embolic events or sometimes per graft, aneurysmal formation.

And, axis related injuries,

Graft Migration

stand graft migration affects approximately 3.6% of patients undergoing evar and it's due to adequate deposition of the stand graft onto the arterial wall.

And management usually is endovascular open, revision.

So what we see here is on a ct, there is a mid abdominal aortic aneurysm that is pretty big.

Involves the SMA and we see that the stent on the coronal images is migrated downward and it's really not covering the aneurysm.

And the same thing you could see on the reconstructions and on ultrasound, again, we see that there is, a flow within the SMA and some flow.

We didn't detect it here, but the stent is not visualized in expected location where the aneurysm is.

Pelvic and Lower Extremity Ischemia

Pelvic ischemia and lower extremity ischemia usually is due to other embolic, event that throws the embol I into the, distal circulation and causes, correspondent injuries.

So in this example, we have, somebody who just had endovascular stent graft repair and on the same day later on complained of loss of arterial pulses in the right lower extremity.

So we did a doppler ultrasound of the right lower extremity and the demonstrated no flow within the SFA and as well as, no spectral, doppler waveforms.

So it was occluded SFA and needed anticoagulation.

Colonic Ischemia

Colonic ischemia happens to up to 3% of cases, and mortality rate is really high.

So, because they develop a gang green of the bowel and they really go into sepsis and, it's really bad outcome.

So it's important to notice this thing.

So this patient had, endovascular 10 graft repair prior to, procedure.

The bowel loops look fine and then post-procedural loops look thickened and the same thing as on the CT pre-procedure bowel loops look good and then post-procedural bowel loops develop, thickening and it's consistent with ischemia.

So that patient, had to go through surgery.

Limb Occlusion

Limb occlusion, can also happen, in patients with a VAR and it happened in up to 5% of patients.

And we divided into the early occlusion or late occlusion.

Early occlusion happens usually in the first few months and, thrombectomy, relining of stent graft with another stent graft or anticoagulation or bypasses, the treatment of choice.

So on this examination, we see that one of the limbs is occluded.

There is no flow on color doppler or spectral doppler, and in the vascular, angiogram is performed that demonstrates no ification of the left, lower extremity system.

Stenosis

Stenosis is another complication that may happen, and it may happen either to one limb or to both limbs, like in this case, and elevated peak systolic velocity as well as alias and will be found on a color and spectral doppler ultrasound.

Noticing this thing also is very important for, patient management.

Loss of Device Integrity

A loss of device integrity could be seen with fractures bend in or bulging of the graft.

So when you see that the shape of the, stent graft is not uniform and there is some bulging, like in this case, it also has to be mentioned and, the surveillance has to pay attention in the next follow up visit when, the, a**l sac is growing and it's, it's a high, possibility of rupture.

So it's a very serious complication and usually due to continuous enlargement of the aneurysmal sac results in, in rupture.

And, most common cause is anoles.

Endoleaks

So we are gonna try to evaluate the anoles, and see how we can divide them.

So type one andic usually is due to inadequate deposition between the stent graft and artery, either in the proximal portion of the stent graft, and that would be type one A or in the distal, portion it would be type one B.

They also, have a, a type one C that is due to inadequate seal of iliac occluded device.

And when type one A is or B is detected, then it requires some repairs.

And this is an example, where we are looking at the transfers image, color doppler that demonstrates that at the most proximal portion of the stent there is extravasation of the color into the aneurysmal sac.

And we see on the spectral doppler that there is a arterialized waveform seen within the aneurysmal sac.

So on the seeing a clip again, you could see that the blood sort of, the color doppler is feeling the aneurysmal sac and also the thrombus looks very, irregular, with lucencies and more higher density material within aneurysmal sac and loosened parts correspond to the, active sort of, blood flow within the sac.

Correlative CTA also shows, the same contrast externalization at the most proximal portion of the stand graft.

And this is another patient on the sagittal view.

You can also see it sometimes and can come from more anterior aspect of the stent and more posterior aspect.

If it's a chimney procedure, then you look where the renal stents are, that's the places where usually end leaks are happening.

Again, we could see the flow.

This is a patient with type one B, where the, endoleak is seen in the distal portion of the stand graft.

Again, correspondent CTAs really confirm the findings on ultrasound.

Type two end OIC is most common occurs on up to two 20 to 30% of patients, and it's the one that persists for, up to six months in 10 to 15% of patients.

So usually we don't do much about it in the beginning unless the aneurysmal sac start to enlarge and, we just observe them.

If it's, anterior feeding vessel is noted, it's usually due to IMA, artery that supplies the aneurysmal sac.

And for if you find the vessels that posteriorly feeding in the vessel, the aneurysmal sac, most likely dealing with the lumbar arteries.

And one of the examples is here we have an aneurysmal sac, that is, on a color doppler demonstrates color flow within, and there is a arterialized wave forms to and fro, within the, aneurysmal sac extending out, outside and shown that this is from the feeding vessel.

And the same is on the sagittal projection here.

This is an aneurysmal sac and we have a flow within it, from the feeding vessel, from the IMA and here it is on A CTA confirms the findings.

And of course we have a, a lumbar artery feeding.

It would be a type two B end leak.

And the vessel, is common, usually posteriorly and fills in the aneurysmal sac posteriorly.

So again, to and fro flow sometimes can be noticed just because it's a sort of retrograde feeling of the aneurysmal sac.

And, interventional images confirm the diagnosis.

Type three end the leaks occurs due to tear in the body of the graft or inadequate deposition of the graft with a native vessel or separation of the components.

Usually again, these patients need a lining the stand graft with a new stand graft components.

So, on the ultrasound examination, gray scale is really paramount.

We could see that there is a dis sort of, there is a tear within the graft, like in this patient posteriorly on the sagittal projection you can also see that there is overlapping of the structures and there is a arterial waveform seen within aneurysmal sac.

So on the CA clip, you could actually see how the, sort of the area of tear is, moving with the blood flow.

And this is another type three endo lake where we have a stand graft.

And if you look in on this images, there is a irregularity of the wall and that's the area where the blood escapes from the stent and fills in the aneurysmal sac.

Again, the thrombus within the aneurysmal excluded portion is very irregular and sort of, different heterogeneities due to, presence of active flow within.

And you could observe on a gray scale how it's pulsating as well.

And, CTA confirms the findings and sometimes it could be really bizarre and leaks and it's really hard to find the source of them.

And like this patient had really what looks like extremely big aneurysmal sac and that this filled with lots of color and on gray scale it's all moving and it's really looked terrible however angiogram was performed and they just couldn't find that much of a leak.

And they thought that the lumbar arteries probably a fill in it.

Type four endo leak is usually caused by too many pores in the graft and occurs intraprocedurally.

So we don't usually see this with ultrasound and endo leak.

Type five is, due to the end detention, again, no identifiable cause is seen and it's diagnosis of exclusion.

Other Complications

So one thing I wanted to just mention that sometimes, infectious processes can also cause complications of EVARs and usually due to like undergoing pro infectious diseases in the abdomen such as appendicitis or diverticulitis, or it could be due to aortic enteric fistula, which most of the times we see on the ct, as an air, within the, aneurysmal sac.

That and the bowel that is adhered to the EVAR.

And usually only a patients with status post evar develop the aortic enteric fistulas on ultrasounds.

Much harder to observe it.

Only if you see like a bowel loop that may be not persin and sort of adherent and not moving much, you can suspect it if the patient is septic aneurysm formation just below the stent graft can also, happen and if it's diagnosed, it has to be mentioned in the report as well because they can also go and, grow and rupture.

And, the axis arterial injury, can be also be found or either like dissections or arterial thrombosis or pseudo aneurysm formation like in this case.

And we can detect the to and pro flow within the neck and YY sun within the, aneurysmal sac.

Summary

So as a summary, I just wanted to say that DOLA ultrasound plays an important role in evaluation and surveillance of aortic pathologists, including AAA and post AA repair and knowledge of anatomy appropriate technique and problem recognition of complication is essential for diagnosis of EVAR.

Complications and ultrasound and CTA are complimentary imaging modality that are great tools for surveillance of patients after EVAR.

Thank you. And we're gonna go.