Pulsatile Internal Jugular Vein

The right internal jugular vein drains blood down from the brain into the superior vena cava and then into the right atrium of the heart. By examining the neck, doctors can see the fullness of the vein and use that to estimate central venous pressure. Elevated venous pressure is one sign of volume overload (essentially a back up of fluid) that can occur with heart failure.

The internal jugular vein runs right next to the common carotid artery so we look at it during every carotid duplex Doppler study. Normally, in transverse view it is nice and flat (as in the image below) or partially filled into an oval like appearance.

The internal jugular vein is fully collapsed atop the common carotid artery. The white outline shows its approximate location.

The internal jugular vein is fully collapsed atop the common carotid artery. The white outline shows its approximate location.

With volume overload, it can puff up like a balloon due to all the blood that is essentially backed up waiting to go through the heart.

The internal jugular vein is filled in the setting of heart failure and volume overload.

The internal jugular vein is filled in the setting of heart failure and volume overload.

Now look at this clip. The internal jugular vein is bounding as it fills and collapses. It is pulsatile (profoundly so).

So what is going on to cause this? I’ll give you a hint: there is something wrong with one of the heart valves. As always, let me know your thoughts.

Kidney Stone?

The vascular lab that develops an expertise in renal artery duplex Doppler will end up visualizing a lot of kidneys. Even though many readers do not have specific training in renal ultrasound, we must be familiar with what is normal and abnormal.

On that note, do you think the bright white signals we seen in this video are renal calculi (kidney stones)?

It turns out there are a number of known mimics of renal calculi. One of the most common is an orthogonal cut of the arcurate artery. Although it appears very echo-bright, as a renal calculi would, it tends to have a three dimensional tubular appearance and that gives it away as a vessel. You will be able to notice that as you watch the video.

The arcuate artery is seen in the cartoon below. It runs between the renal cortex and the renal medulla.

Cartoon of a kidney demonstrating the arterial anatomy.

Cartoon of a kidney demonstrating the arterial anatomy. J Ultrasound Med 2004; 23:1361-1367

This article is a very nice review on the topic and gives examples of a number of mimics of renal calculi:  J Ultrasound Med 2004; 23:1361-1367

  • arcuate artery
  • segmental artery
  • prominent papillae
  • milk of calcium cysts
  • prominent junctional parenchymal line
  • angiomyolipoma
  • foreign body

The more you see, the more you know.

mid aorto syndrome trans 2_cropped

Mid Aorta Syndrome

In this example, a renal artery duplex Doppler was ordered as part of an evaluation for difficult to control hypertension. Renal artery stenosis is a less common cause of hypertension but was felt to be a possibility in this case given that it was of early onset and difficult to control.

Immediately, the study revealed something.

Proximal abdominal aorta in long view. Flow is turbulent, hight velocity and has a prolonged acceleration time. All signs point to a more proximal obstruction.

Proximal abdominal aorta in long view. Flow is turbulent, hight velocity and has a prolonged acceleration time. All signs point to a more proximal obstruction.

Flow in the aorta was high velocity, turbulent and showed a delayed acceleration time also referred to as a tardus et parvus appearance. All this points to a stenosis more proximal (before the point of observation).

As expected, flow in the renal arteries and the renal parenchyma had post obstructive features.

Tardus parvus flow in the renal parenchyma reflects delayed filling from the obstruction in the aorta.

Tardus parvus flow in the renal parenchyma reflects delayed filling due to the obstruction in the aorta.

This led to a CT that nicely demonstrated the distal thoracic aorta stenosis and abnormal aorta wall thickening.

mid aorto syndrome trans 2_cropped

Distal thoracic aorta with small lumen and thickened wall.

An immediate question comes to mind: what caused this thoracic aorta stenosis? Additionally, is the diminished flow to the kidneys contributing to the hypertension?

These are, of course, good questions. Tell me what you think.

The “Good” Vascular Lab

A good vascular lab strives to deliver a high quality study with an accurate interpretation. This should be done in a professional and patient centered environment and, of course, done efficiently. When this happens, the lab provides reliable information for the patient and the referring physician that can be used to assist in determining a diagnosis and developing a treatment plan.  Seems pretty obvious right?

Hidden in there is the subtle concept appropriateness. An appropriate test is truly necessary and, based on the current evidence or understanding of a disease, provides information necessary to make important decisions about care – decisions that lead to a meaningful impact on  the health and well-being of the patient.

In other words, a high quality study with accurate results that do not inform patient care in a meaningful way could be described as inappropriate, unnecessary and even wasteful.

The appropriate use of medical care has a number of champions. Relevant to diagnostic testing, the Choosing Wisely program’s goal is to promote patient and physician discussions that are “necessary to ensure the right care is delivered at the right time.” They encourage medical societies to point out unnecessary testing that should be avoided. The ABIM Foundation initiated the program as part of their mission to inject “medical professionalism into clinical policy and practice”. By my understanding they favor accountability, evidence-based medicine and teamwork and shared responsibility in delivering health care.

Representing vascular testing, the Society for Vascular Medicine published Five Things Physicians and Patients Should Question in Vascular Medicine. Additionally, appropriate use criteria for peripheral vascular testing have been published.

Ultimately, the vascular lab has the responsibility to help providers understand when testing is appropriate for their patients and at the same time discourage unnecessary or inappropriate tests. This can create a conflict of interest particularly in a fee for service environment. Regardless, I suggest it is the right way to practice medicine and a step in the right direction toward higher quality care.

If vascular testing is part of what you do for a living or is suggested for you by your doctor, take a look at the linked resources and be mindful of appropriateness.

Do you disagree? Have further thoughts? Feel free to let me know.

Subclavian Steal

This first picture is a normal vertebral artery waveform. Compared to the next one (which is abnormal) it is easy the see a difference. In the abnormal one, the flow dips down to baseline immediately after systole. The pattern created is called a “bunny waveform” for resembling a crouched rabbit as viewed from the side.

Normal vertebral artery waveform. Sharp upstroke and a good amount of diastolic flow typical for an artery feeding a low resistance vascular bed (the brain).

Normal vertebral artery waveform. Sharp upstroke and a good amount of diastolic flow typical for an artery feeding a low resistance vascular bed (the brain).

After the systolic peak, there is a severe drop in flow velocity. The resultant waveform resembles a crouched rabbit from the side - head to the right.

After the systolic peak, there is a severe drop in flow velocity. The resultant waveform resembles a crouched rabbit from the side – head to the right.

How does this happen? The left vertebral artery takes off from the left subclavian artery just after its origin. A stenosis in the origin of the subclavian artery is the culprit. A stenosis (narrowing) accelerates blood flow. In order to keep the same amount of blood flowing through a smaller opening everything has to move faster. By Bernoulli’s principle, higher velocity flow has a lower pressure and as we have discussed in prior posts, blood always flows toward the low pressure/low resistance vascular beds. To bring it all together, just at the peak of systole, blood flow is fastest through subclavian stenosis and pressure is lowest – low enough in fact to cause blood to flow backward from the vertebral artery into the low pressure zone. In other words, blood is stolen from brain into the arm.

In mild subclavian stenosis, the pressure differential is only great enough at peak systole, when velocity is highest, to elicit a dip in flow in the vertebral artery. The post systolic dip, as I call it, or the “bunny” waveform as others call it is formed.

As subclavian stenosis worsens, the pressure differential grows larger and lasts longer through the cardiac cycle. Flow reversal becomes more and more prominent making forward flow during systole and reversed flow in diastole (so called “to and fro” flow). Eventually, there is constant reversed flow when the subclavian artery is occluded.

A more significant steal. Blood from drops and then reverses in the vertebral artery during most of systole.

A more significant steal. Blood flow velocity drops and then reverses in the vertebral artery during most of systole.

What does all this mean for patients? First and foremost, as a clinical effect of atherosclerosis, it defines people at higher risk for things like stroke and heart attack. And, as discussed previously, those patients may benefit from treating their vascular risk factors of smoking, diabetes, cholesterol, blood pressure with medication, diet and exercise. We suspect that most patients with mild subclavian stenosis and bunny waveforms in the vertebral artery never notice it.

In uncommon situations the blood that is stolen from the brain through the vertebral artery can cause neurological symptoms such as vertigo, passing out, blurry vision or slurred speech. Usually for this to happen there has to be something else affecting blood flow to the brain such as an occluded carotid artery or very low blood pressure from shock, dehydration or sepsis.

Interestingly, I have seen patients with subclavian steal who developed neurological symptoms while on dialysis. Can anyone explain why?

Carotid Spectral Doppler Waveform in Heart Failure

The hemodynamics of advanced heart failure are quite complex. In this post, I present a visual demonstration of some of these changes by looking at the carotid artery spectral Doppler waveform in advanced heart failure.

To begin let’s look at normal. The brain maintains a continuous supply of blood throughout the cardiac cycle. Thus, there is forward flow through systole and diastole in the carotid arteries. The spectral waveforms in the image below show this well. The brain does this by maintaining a low vascular resistance. Just like water finding the easiest path down hill, blood finds the easiest path to follow in the body. The brain makes it very easy for blood to flow into it; probably because it considers itself a vital organ.

Normal CCA spectral waveform. The flow continues throughout the cardiac cycle (from beat to beat) and never goes below the baseline (never reverses).

Normal CCA spectral waveform. The flow continues throughout the cardiac cycle (from beat to beat) and never goes below the baseline (never reverses).

In sharp contrast to normal shown above, in advanced heart  failure we can see a reversal of flow immediately after systole that is striking in appearance if you are accustomed to the normal waveforms.

The flow reversal is marked in this image. The triphasic waveform resembles peripheral vascular flow.

The flow reversal is marked in this image. The triphasic waveform resembles lower extremity peripheral vascular flow.

The post-systolic dip is still evident in the internal caroid artey; although there is no longer any significant flow reversal.

The post-systolic dip is still evident in the internal carotid artery; although there is no longer any significant flow reversal.

chf waveforms vert16_cropped

Not surprisingly, the post-systolic dip and flow reversal are present in the vertebral artery as well.

So, why do we see this waveform in advanced heart failure? Frankly, I don’t know for sure. I suspect it is a combination of effects including increased vascular stiffness and aortic valve dysfunction in dilated cardiomyopathy. Regardless, it is a good visual example of the altered hemodynamics of heart failure. I welcome your thoughts and ideas.

 

 

Abdominal Vascular Anatomy

Duplex Doppler ultrasound is an important tool to assess the abdominal vasculature. Examples include abdominal aortic aneurysm (AAA) screening, evaluating for renal artery stenosis, ruling out pelvic deep vein thrombosis (DVT) and sorting out aorta-iliac occlusive disease. Keys to a good study include modern equipment, patient prep  (fasting, cooperative and not too overweight) and most importantly, tech skill and experience. Knowing ultrasound anatomic landmarks will get you a long way to better performing and interpreting these studies.

The following clip is an example of pretty well visualized abdominal vascular anatomy. The image is a sweep in transverse of the entire abdominal aorta from the celiac axis to the bifurcation into the iliac arteries. As you watch the clip, learn to recognize the major vascular landmarks.

First, the celic artery comes off the aorta anteriorly (heading up). It splits into the hepatic branch (image left, patient’s right) and the splenic branch (image right, patent’s left). Next the superior mesenteric artery (SMA) comes anteriorly off the aorta and then turns 90 degree running down the length of the proximal aorta. At the same time, the left renal vein comes under the SMA and over and across the aorta joining the inferior vena cava (IVC) on the other side. At this moment, at about 9 o’clock, the right renal artery takes off laterally and runs under the ICV (looks like it is running into it) to the right kidney.  Just a bit later, the left renal artery takes off laterally from about 4 o’clock and runs straight to the left kidney. All this time, the aorta remains just right of midline (sitting to the right of and on top of the vertebral bodies) as the IVC migrates deep and eventually under the aorta at the point where the aorta bifurcates (splits) into the right and left iliac arteries in the pelvis. At some point, the inferior mesenteric artery has taken off from about the 2 o’clock position – this can be difficult to see.

To solidify this in your mind, it takes knowledge of cross sectional anatomy and the ability to imagine a 3D image as you follow the course of an artery in 2D. Eventually, you will have a strong grasp of this anatomy and be able to follow landmarks in any abdominal vascular ultrasound.

Carotid Plaque Appearance

The presence of carotid artery plaque is associated with cardiovascular risk including stroke and heart attack. In patients with enough carotid plaque to cause stenosis, intervention with surgery or stenting can help prevent further strokes for those who have had a previous stroke or temporary ischemic attack (TIA). This recent review article covers the topic well.

The article also summarizes the data showing that not all plaque behaves the same. It looks like the echo-appearance of plaque is probably important for further risk stratification. Size and specific B mode ultrasound characteristics identify plaque that is more associated with stroke risk or even other cardiovascular risk. How do we characterize plaque in vascular ultrasound?

It’s really a simple description of what we see. As with most things in vascular ultrasound, it is dependent on good images obtained with ideal settings that gives good resolution and an accurate representation of what is there.

Size: Small, Moderate or Large amount.

Location: Common carotid, bifurcation, internal carotid or external carotid.

Homogeneous – Has a consistent echo-texture. Use the normal thyroid gland echo-texture as a reference.

Heterogeneous – Has a mixture of bright and dark areas with some calcification often present.

Echolucent – Very echodark – almost “invisible”.

Calcified – Very echobright with shadowing that can limit visualization.

Smooth – Plaque surface is smooth.

Irregular – Plaque surface is jagged and complex appearing.

Ulcerated – 2 x 2 mm crater with flow demonstrated filling into the space.

These descriptions are of course very subjective. More objective measures such as computer aided analysis of B mode features, 3D assessment of plaque area and volume and PET and MR features are worth paying attention to as we learn more about these techniques.

Let’s look at some examples: (click to see larger images)

nml bulb ica5_cropped

In the above image, there is no plaque or intima media thickening. Plaque is defined as a focal protrusion into the lumen that is at least 50% thicker than the surrounding area. Plaque is also defined as intima media thickness exceeding either 0.12 or 0.15 cm (depending on which consensus paper you look at).

smooth hetero5_cropped

This image shows a moderate amount of smooth heterogeneous plaque in on the near wall of the carotid bifurcation extending into the proximal internal carotid artery.

moderate irreg hetero18_cropped

Here is a moderate to large amount of irregular appearing heterogeneous plaque with focal calcification (bright areas with shadowing) in the bifurcation extending into the proximal to mid internal carotid artery.

complex irreg plaque bulbe5_cropped

Look how complex and irregular appearing this plaque is.

homogeneous echolucent plaque20_cropped

This images uses color Doppler flow to outline the plaque and highlights the highly echolucent (dark) component.

r bulb ulcer plq4_(60)_cropped

r bulb ulcer plq6_(237)_cropped

In this set of images there is an ulcerated plaque in the far wall of the carotid bifurcation. We see it clearly in B mode and see the color Doppler filling thus confirming it is an ulcer.

These images demonstrate how varied plaque appearance can be. Does characterizing the plaque like this help us take better care of patients? Good question. Although we have a good amount of data associating more complex plaque and rapid plaque growth by area with risk of stroke and heart attack, we do not yet know if or how to treat those patients differently to decrease the known risk. Stay tuned as the data evolves!

AAA Screening

Based on cost effective lifesaving, the USPSTF recommends screening for abdominal aortic aneurysm (AAA) in all men aged 65-75 who have ever smoked. The idea is that aneurysms can be found early and monitored. Many will not change much but a few will grow bigger to the point they are at risk for rupture. At that point, when the risk of rupture exceeds the risks of intervention, they can be fixed.

Fortunately this is a fairly straightforward exam to perform and interpret and one that is not too onerous for patients.The majority of exams are normal.

In general, we look at the diameter of the abdominal aorta from its origin at the celiac axis to its bifurcation. We also look at the iliac arteries. We characterize any plaque we see and look at the flow and velocities in the aorta and the iliac arteries. Patients need to be fasting to cut down bowel gas and the exam takes about 20 minutes.

So what do we  see?

Normal size aorta in long view. (click images to enlarge)

nml aorta15_cropped

Moderate aneurysm

AAA tran8_croppedAAA long10_cropped

Large Aneurysm with thrombus

aaa thrombus trans9_croppedaaa thrombus long16_cropped

 

What do we do when we find an aneurysm? The best follow up protocol is still being sorted out. Currently we follow these recommendations but will individualize them as necessary.

  • <3.0 cm              no further imaging necessary
  • 3.0 – 4.4 cm        recheck every 2-3 years
  • 4.5 – 5.4 cm        recheck every 6-12 months
  • >5.4 cm              refer to consider treatment

Large AAAs can be treated with either surgery or endovascular stent grafting.

Patients are of course counseled to live a healthy life style including no smoking, moderate exercise, a healthy diet. We don’t yet have good evidence for how to treat AAAs with medication. Regardless, we work with patients to treat cardiovascular risk factors including high cholesterol, high blood pressure and diabetes.

Aortic Dissection

While working in the lab one day, my tech calmly told me he needed to stop the carotid exam he was performing as the patient was having chest pain. I looked up from my desk to see this loop playing on the machine.

Aortic dissection is not often discovered during a carotid duplex. However, in one series, 40% of aortic arch dissections enter the CCA Stroke 1988;19:970-6. In this case, the patient was being evaluated for chest pain and referred for a right carotid bruit – aortic dissection had not been suspected at that time. Upon seeing an acute appearing dissection of the common carotid artery, we worry it may originate from the aorta and urgently have the patient evaluated for aortic dissection.

We informed the primary team and they arranged urgent CT, cardiothoracic surgery consultation and operative repair the next morning with, thankfully, good outcome.

In this recent review of common carotid artery dissection 46 cases were found in the literature since 1960. Of those, 25% originated from the aortic arch. “The most common presenting neurologic symptoms were hemiparesis, decreased consciousness, headache or neck pain, aphasia and monocular vision loss.”  Journal of Stroke and Cerebrovascular Diseases 2012;21:52-60. Our patient presented with chest pain.