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)
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).
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.
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.
Look how complex and irregular appearing this plaque is.
This images uses color Doppler flow to outline the plaque and highlights the highly echolucent (dark) component.
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!