ExtraCranial Carotid Ultrasound:Diagnostic Nuances - SD

Introduction

My name is Gretchen a w Gooding.

I am professor of radiology at the University of California San Francisco and I'm chief of radiology at the Department of Veteran Affairs Hospital in San Francisco.

And I'm going to speak today about extra cranial carotid ultrasound and the diagnostic nuances involved in that.

Carotid ultrasound is a common disease, particularly in elderly men, especially those who have been, had a history of smoking and diagnostic ultrasound plays a really important role in deciding which patients can benefit from surgery or stenting and which patients are relatively normal.

So it's an excellent screening test and that's what I'm going to discuss today.

The topic today is extra cranial carotid ultrasound diagnostic nuances.

Initial Gray Scale Imaging and Intima-Media Thickness

It is important in doing carotid ultrasound that the initial study is a gray scale image of the carotid artery to determine the intimate media thickness and to look for the presence of plaque in the carotid.

So in this example, you see a intermediate thickness of 0.076, which would be normal in an elderly patient.

A 0.05 centimeters would be normal in a youngster.

And here on the opposite side is thickening of the intimate media, and this kind of thickening is usually related to smoking.

Now in this instance, the intimate media is incredibly thickened on the anterior side, and this patient gave a history of being at ground zero for the atomic bomb tests in the D Nevada desert.

In the 1940s, radiation will cause remarkable thickening such as you see here.

Presence and Characteristics of Plaque

The next thing you want to determine is the presence of plaque and plaque is usually homogeneous and felt to be relatively stable or heterogeneous as you see in this case.

There is relatively homogeneous area here, but a hypo coic area here suggesting the presence of intra plaque hemorrhage and therefore instability in this patient who has a 70 to 90% stenosis by peak systolic velocity, but only a 50 to 69% stenosis by end diastolic velocity.

The presence of intra plaque hemorrhage may indicate to the surgeon that he would be more apt to intervene with, endarterectomy or stenting because of this possible instability.

And that would perhaps indicate to him that he would do the surgery before he might otherwise.

Normal Carotid Bulb and Sensitivity to Massage

Here is a nice example of just a normal bulb with regular rhythm and normal velocity.

You see the first peak in systole is higher than the second peak.

Keep in mind when doing carotid ultrasound that some patients have a great sensitivity to carotid massage up at the area of the bulb where the chemoreceptors exist.

And you see here on the right you have a normal velocity, and on the left you see in the same patient that the flow is significantly slower.

And in patients who have a great deal of carotid sinus hypersensitivity, they can even faint if too much pressure is put on the bulb.

So you need to tread lightly with these particular patients.

Tachycardia and Its Effects

Here is an opposite finding, which is tachycardia.

This patient has about 117 beats per minute, and that may elevate systolic velocity into the moderate range.

Usually end diastolic velocity will remain below the normal of less than 40 centimeters per second.

Patients with tachycardia may simply be, tachycardia because of exercise, perhaps because of anemia, but also consider hyperthyroidism and one can simply move the transducer quickly over to the thyroid to look for, a thyroid inferno vascular pattern.

In patients with hyperthyroidism and Graves disease, turbulence tends to occur at the origin of the common carotid arteries and at the dilated bulbus areas of the carotid.

And when one has turbulence, it tends to elevate the peak systolic velocity, which you see here ranging, about 148 centimeters per second.

It tends to elevate the peak systolic velocity to a moderate range while maintaining a normal diastolic flow.

Waveforms in Common, Internal, and External Carotid Arteries

Now let's think about some waveforms that we might have in the common carotid artery or the ICA, the internal carotid or the external carotid artery.

One of the more common abnormal waveforms is that of a low velocity profile unilaterally with tardis parvis waveforms.

When you see a TARDIS parvis waveform that suggests a more proximal stenosis and it looks like little pyramids, the waveform is slow to rise to peak and the waveform is never very high.

Parvis meaning small.

Tardus Parvus in Proximal Stenosis

Here is an example where tardis parvis comes into play.

The patient's has a critical proximal internal carotid artery stenosis with a peak systolic velocity of 430 centimeters per second.

So this is a critical stenosis and beyond that, in the distal internal carotid artery, the flow is only 22 centimeters per second and you see that it is slow to rise and that the peak and end diastolic velocities are really low compared with the area of stenosis.

So this is simply a reaction to a critical stenosis with a tardis parvis wave form.

Beyond it, here is an example of a patient who has tardis parvis waveforms in the external carotid artery and in the internal carotid artery, as you see here, the velocities are normal, but there is a delay to peak systole.

You see, it's like someone's blowing this waveform over.

Peak systole takes this much time to develop.

And over in the mid ICA it's taking quite a while to reach peak in patients who are going to have an A VR replacement.

Obviously they have aortic stenosis and or aortic insufficiency, and this is the kind of a waveform you might see rather than just the classic TARDIS parvis waveform.

This is basically a TARDIS waveform without the parvis portion.

Bilateral Low Velocities

Another thing to remember is that when you have bilateral low velocities in the common carotid, the internal or the external carotid artery, you should consider the patient may have aortic stenosis, he could have hypertrophic cardiomyopathy or a less likely possibility would be to consider bilateral origin stenosis of the common carotid artery.

So after you have thought about that, let's think about this particular waveform, which is a common one in elderly males that of atrial fibrillation.

Atrial Fibrillation

This produces an irregularly irregular rhythm with peak tope variation.

Here is one peak relatively high.

Here is one relatively low and the other abnormality is that there is a relatively rapid second beat at this point and a relatively, distant peak from here.

So there is peak to peak variation and the technologist of course then has to pick out something that reflects a kind of an average velocity.

So there may be some variability from exam to exam because of this rhythm.

Abnormality, pulse's, alternates is another rhythm abnormality In this instance, the patient has both strong followed by weak cardiac contractions and it indicates that there is a severe impairment of left ventricular function.

So on the examination that you see here, you have a peak systolic velocity that is high, and then you have a second peak systolic velocity that is quite low.

Aortic Regurgitation

Another finding in, rhythm abnormalities is aortic regurgitation.

Aortic regurgitation as a single entity is not nearly as common as aortic stenosis and it tends to produce if it's really severe, a reversed flow throughout diastole.

That particular finding suggests aortic insufficiency when you see it in all the arteries in the body.

A two and fro waveform is also seen in pseudo aneurysm, but in those instances of pseudo aneurysm, the two and fro waveform is only in that particular site.

Bisferiens Pulses

BIS variance pulses.

In this case, there is a second systolic peak that is higher than the first systolic peak.

It's usually a sporadic sign.

It doesn't occur in every image, but it also suggests aortic valve disease.

It is also seen normally in the bulb commonly, so it probably also occurs simply because of an elevated AP diameter.

But if you see it in a number of pictures in your study, then you can at least suggest that there may be, aortic valve disease as an etiology.

If I just see it once or twice, I don't usually comment on it.

Intraaortic Balloon Pump

An intraaortic balloon pump.

These patients are patients that are seen in the ICU very seriously.

Ill usually, and these waveforms are typically really unusual excursions both above and below the baseline and not only in the carotid but in all the arteries.

And you may not have the history of intraaortic balloon, the clinicians may have failed to tell you that.

And when you see this really unusual two and fro waveform patterns, that suggests that you're dealing with intraaortic balloon.

Progression of Internal Carotid Artery Disease

Now let's talk a little bit about the internal carotid artery and its progression of disease from critical to near occlusive.

As you see here on the left, the patient has a high peak systolic velocity of 380 and a high end diastolic velocity of 1 46.

And over, time you see that the patient's peak systolic velocity has progressed.

But instead of the peak systolic velocity rising, since it's now a greater than 95% occlusion, the peak systolic velocity actually has fallen and end diastolic velocity is zero.

So the waveform has converted from an organ flow like waveform with critical stenosis to a dampened resistive waveform, which is the kind of a waveform you get before the patient actually occludes the vessel.

Diagnosis of Distal Occlusion

What is the diagnosis In this case?

This patient has a waveform taken in the mid common carotid artery and you see there is a good peak systolic upsweep, but end diastolic is very low.

What does that indicate?

Well, usually it indicates that there is a distal occlusion either in the internal carotid artery or perhaps even you might get it from a very serious, dissection of the internal carotid artery which is causing occlusive, a problem.

So as we noted on the left, we have a mid common carotid artery waveform that is highly resistant.

That is the diastolic component is remarkably low and that indicates that there is actually a more distal occlusive problem.

And here we see on the right that the left proximal internal carotid artery has occluded.

Now if you look at the common carotid artery in this instance, which is normal, is the left normal with an end diastole of six or is the right normal with an end diastole of 17?

Well, again, this patient needs organ flow perfusion to the brain and the picture on the left indicates a high resistance.

And high resistance, as we mentioned, indicates a distal obstruction such as an ICA occlusion.

So in this instance, the left is abnormal and the right is normal.

And here we see the left again with low diastole in the proximal common carotid artery and absent flow in the internal carotid artery Because of occlusive disease now and out of the field, ICA occlusion would look like this, you have a highly resistive waveform in the midcom carotid artery with only a nine centimeter per second and diastole.

And on the examination of the internal carotid on the in the mid portion, you see this highly resistive waveform, but there is flow in it.

It's not occlusion at the mid internal carotid artery.

There has to be a more distal occlusion and it might be in the cavernous sinus or it could be distal end, artery disease in the head that is producing this particular waveform, highly resistive in both the common and in the internal.

Vertebral Artery Compensation

Now, what happens to the vertebral artery when the ICA is resistive, as you see on the left resistive and abnormal?

Well, the vertebral artery compensates on that side and it is causing a remarkable rise in peak systolic velocity.

The normal vertebral artery in on average is about 44 centimeters per second, and in this case it's about four times that.

Alternating Flow and Innominate Artery Occlusion

What does alternating flow in the internal carotid artery indicate?

What is the diagnosis?

It is a nominate artery occlusion.

The right carotid artery in this instance alternates flow to feed in one part of the cycle, the arm, and in the other part of the cycle the brain and in addition, flow tends to be low in the right carotid artery because the flow that it is getting is feeding from a reverse vertebral artery.

And also you may have reversal of flow in the external carotid artery with an innominate artery occlusion.

So to keep track of all these findings, a nominate artery occlusion is associated with reversal of the right vertebral artery, a contr lateral velocity increase in the carotid to take on the flow that can't get up through the occluded denominate and an IPS lateral philosophy that alternates as we showed, and an ipsilateral ECA that may alternate to try to increase the flow to the internal carotid artery.

So it's a very specific group of findings, a nominate artery occlusion.

Common Carotid Artery Occlusion

Now what about common carotid artery occlusion as you see here, what are you likely to see in the internal and external carotid in this situation?

Well, you look for reversal of the external carotid artery that feeds the internal carotid artery and the external carotid artery loses its typical resistive waveform and internalizes so that even though it's reversed, it will look very much like an ICA.

And here is such a picture.

You see the ECA is blue and the ICA is a forward flow.

So the ECA is reversing to fill the internal carotid artery because the common carotid artery is occluded.

In this particular instance, you see a TARDIS parvis waveform in the external carotid artery because both the ICA and the CCA happen to be occluded in this patient.

And the only flow getting to the ECA is from collateral flow in the neck.

Other Disease Entities

Carotid Dissection

Carotid dissection is another entity to be on the alert for.

This occurs in young adults primarily with little or no plaque that really separates them from an older group who have plaque.

The ICA tends to taper from the dissection, which may begin at the skull base and descend.

This flow is also highly resistant and in the common carotid artery dissection, if it's acute, you may actually see motion of a flap.

This is an example of carotid dissection extending from the aorta and it is a chronic dissection.

So what the image is circling is a hypo coic area of thrombus plaque that is formed.

There's no longer a mobile flap, so this is several years old at this point in time.

Fibromuscular Dysplasia

Now, fibromuscular dysplasia of the carotid usually isn't a young woman involving the renal arteries most commonly, but the internal carotid artery.

Second most commonly, and in this case you see these little bobas dilatations along the track of the carotid artery in arterial venous fistula of the carotid.

Arteriovenous Fistula

Usually it's a traumatic event.

It causes low resistance flow of high velocity throughout the entire cycle with arterial peaks and flow both above and below the baseline.

Here's an example of a carotid arterial venous fistula.

The artery communicates with the vein.

You have very high velocity in peak systole and in this case, some elevation of diastole, not as much as you may see in other cases, but this is a classic arterial venous fistula.

And you can actually see the fistula.

Site two and fro flow is a very important kind of flow to identify.

Remember we mentioned that if you see it throughout the arterial system that it's may be related to aortic insufficiency, but when you see it fally, it is related to a pseudo aneurysm.

Pseudoaneurysm

And in this case, in the carotid, there was an emergency request for an expanding mass in the neck following instrumentation.

And you see the false aneurysm and the typical two and fro flow that it produces.

A carotid pseudo aneurysm is a pulsating hematoma.

It connects with the artery and there is two and fro flow both above and below the baseline as you see in this illustration.

Here is another example of the classic two and fro flow In a carotid pseudo aneurysm,

Moyamoya Disease

a more unusual disease is called carotid moyamoya disease.

In this instance, the internal carotid artery has severe stenosis and there is occlusive disease terminally in the brain with fine collateralization in the brain.

So you have end stage disease in the internal carotid artery throughout in the neck.

The ICA smoothly tapers from the bulb.

The ICA is smaller than the ECA and it has a very resistive waveform.

This disease usually occurs in Asians or in children with sickle cell disease.

Takayasu Arteritis

On the other hand, another unusual disease is carotid SSU arteritis.

It is an idiopathic granulomatous arteritis that affects young Asian women with, transient ischemic attacks or actual stroke.

And the characteristic of this finding is a uniformly thickened carotid wall throughout the common internal external carotid

TAUs Arteritis also occurs in a young group less than 40 years old, and it is associated with a decreased brachial artery pulse difference of, a greater than 10 millimeters of mercury systolic between the two arms.

And there is a treatment for this disease and that is steroids.

Bilateral High Resistance

Now, what catches your attention when you see these pictures?

These are the values obtained on the right and on the left.

And what I am trying to point out is that the diastolic velocity is low.

In other words, both sides have relatively high resistance in all the vessels.

And that would indicate when you have reive changes throughout either low and diastolic velocity in the C-A-I-C-A invertebrate arteries suggesting increased intracranial pressure or a diffuse intracranial process such as a vasculitis.

So keep that in mind. On the other hand, if you had elevated diastolic flow, really high diastolic flow throughout, that would indicate something like maybe an AAV m in the head.

Vascular Steal

This is an example of a vascular path, a 50-year-old woman with an occluded right internal carotid artery, and she has bilateral vertebral artery steel disease with reversal of the vertebral flow on both sides.

What about that entity?

Carotid Body Tumor

The carotid body tumor, this is a highly vascular mass at the bifurcation of the internal carotid and the external carotid arteries.

It's a paraganglioma, it's rare, it can be familial.

And here's an example.

You see how this carotid body tumor really causes the internal carotid artery to arc way up.

This is a very large one, a nonfamilial one that is stretching the bifurcation.

Treatment Considerations: Endarterectomy vs. Stenting

Now as to treatment when the patient has a serious stenosis of greater than 70%, then endarterectomy versus stenting is one of the considerations.

A recent journal article in the New England Journal suggested that patients for endarterectomy had a 3.9% 30 day stroke or death while that for stenting was much higher.

But you have to consider that this paper is the early, early experience with stenting.

And as experience is gained, I'm sure that this, complication rate for stenting will drop precipitously.

Endarterectomy is not a completely benign procedure in this case.

There's an example of a complication shown at the time of surgery where the distal internal carotid artery has a critical stenosis post endarterectomy.

And so this requires reoperation before the patient is closed.

Here's another example of an intraoperative ultrasound post endarterectomy complication, and that is a carotid dissection.

This also needs to be repaired.

And finally, another ICA mobile flap.

In the intraoperative period that has been repaired, as you see on the right now,

Postoperative Complications

the postoperative patient with a carotid endarterectomy may develop a stenosis within the first year most commonly.

But here is an example of a severe stenosis, three years prior.

And, here is a carotid stent that the velocity is 800 centimeters per second and following the stent it's only 98 centimeters per second.

So a dramatic drop and a successful stenting.

Here's an example of a stent where the proximal portion of the stent is not really fixed well into the wall.

This patient has been followed now for over a year without any adverse effects to date, but there is still concern about that proximal attachment.

Medicare Physician Quality Reporting Initiative

Finally think in terms of, the new Medicare Physician Quality Reporting Initiative.

This is a professional billing, as of 7 1 0 7 that will give increased reimbursement for a quality measure.

And for those of you who are doing carotid ultrasound, you should add to your dictations that measurement of carotid stenosis is based on velocity parameters that correlate the residual internal carotid diameter with the North American symptomatic carotid endarterectomy trial based on stenosis levels.

Temporal Arteritis

Finally we have an example here of temporal tapping of the superficial temporal artery in the external carotid artery.

And as you are well aware, temporal arteritis affects the superficial temporal artery.

And ultrasound is a good way to show that circumferential hypo coic area around the transverse superficial temporal artery with a high specificity and sensitivity for the diagnosis of temporal arteritis, which can be treated with steroid therapy.