biology

Intima–media thickness

Intima–media thickness is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Intima–media thickness rather than just read about it. In short: Intima–media thickness (IMT), also called intimal medial thickness, is a measurement of the thickness of tunica intima and tunica media, the innermost two layers of the wall of an artery. The measurement is usually made by external ultrasound and occasionally by internal, invasive ultrasound catheters.

Key takeaways

Intima–media thickness belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Intima–media thickness to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Intima–media thickness from memory before moving on to harder problems.

Reference excerpt

Intima–media thickness (IMT), also called intimal medial thickness, is a measurement of the thickness of tunica intima and tunica media, the innermost two layers of the wall of an artery. The measurement is usually made by external ultrasound and occasionally by internal, invasive ultrasound catheters. Measurements of the total wall thickness of blood vessels can also be done using other imaging modalities. Carotid IMT is used to detect the presence of atherosclerosis in humans and, more contentiously, to track the regression, arrest or progression of atherosclerosis. Ultrasound measurements of carotid IMT were first proposed and validated in vitro by Paolo Pignoli in 1984 and further details were subsequently published in a highly cited article. The use of IMT as a non-invasive tool to track changes in arterial walls has increased substantially since the mid-1990s. Although carotid IMT is predictive of future cardiovascular events, the usefulness of measuring change in carotid IMT over time is disputed, as meta-analyses have not found that change in carotid IMT is predictive of cardiovascular events. As such, the use of change in carotid IMT as a surrogate endpoint measure of drug efficacy in clinical trials, or in clinical management of cardiovascular disease, is debated. Carotid IMT is occasionally used in clinical practice, but its role is not clear. After systematically reviewing the evidence base, the United States Preventive Services Task Force found no support for its routine use in stratification of risk for people at intermediate cardiovascular risk. However, in 2003 the European Society of Hypertension–European Society of Cardiology guidelines for the management of arterial hypertension recommended the use of carotid IMT measurements in high-risk patients to help identify target organ damage and in 2010 the American Heart Association and the American College of Cardiology advocated the use of carotid IMT on intermediate risk patients if usual risk classification was not satisfactory.

Measurement of IMT IMT can be measured using external ultrasound in large arteries relatively close to the skin (e.g. the carotid, brachial, radial, or femoral arteries). External ultrasound methods have the advantage of being non-invasive, comparatively low cost and convenient. Deeper internal arteries, such as the coronary arteries require special intravascular catheters employing ultrasound or optical coherence tomography to measure IMT. The carotid artery is the usual site of measurement of IMT and consensus statements for carotid IMT have been published for adults and children. Often, carotid IMT is measured in three locations: in the common carotid artery (typically at one cm proximal to the flow divider), at the bifurcation, and in the internal carotid artery. IMT measurements of the far (deeper) wall, by ultrasound, are generally considered more reliable than measurements performed on the near (more superficial) wall; although measurement of both near and far wall IMT has also been advocated. Carotid IMT has been used in many epidemiological and clinical studies and these have shown associations with several risk factors, including type 2 diabetes, familial hypercholesterolemia, high-density lipoprotein cholesterol (HDL-C), triglycerides, rheumatoid arthritis, non-alcoholic fatty liver disease, and air pollution. Since the 1990s, some clinical trials of lifestyle and pharmaceutical interventions have also used carotid artery IMT as a surrogate endpoint for evaluating the regression and/or progression of atherosclerotic cardiovascular disease; however the appropriateness of carotid IMT in this context is uncertain. Although carotid intima–media thickness is strongly associated with atherosclerosis, thickening of the intima–media may not always be due to atherosclerosis. Intima–medial thickening is a complex process, depending on a variety of factors, including blood pressure, local hemodynamics, shear stress and circumferential tensile stress. Variations in IMT between different locations (e.g. the common carotid artery, the carotid bulb and the internal carotid artery) may reflect differences in local hemodynamic forces.

References

Various Newscasts on Carotid IMT (Intima Media Thickness) Archived 2009-07-17 at the Wayback Machine Bortel L (2005). "What does intima–media thickness tell us?". Journal of Hypertension. 23 (1): 37–39. doi:10.1097/00004872-200501000-00009. PMID 15643121. Wong M, Edelstein J, Wollman J, Bond MG (1993). "Ultrasonic-pathological comparison of the human arterial wall: verification of intima–media thickness". Arterioscler Thromb. 1 (4): 482–486. doi:10.1161/01.ATV.13.4.482. PMID 8466883. Saba L, Sanfilippo R, Montisci R, Mallarini G (Feb 2010). "Carotid artery wall thickness: comparison between sonography and multi-detector row CT angiography". Neuroradiology. 52 (2): 75–82. doi:10.1007/s00234-009-0589-5. PMID 19727693. S2CID 7575821.

Illustrations

Worked examples

Example 1 — a first encounter with Intima–media thickness

Start with the simplest possible case. Write down what Intima–media thickness claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Intima–media thickness before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Intima–media thickness ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Intima–media thickness

In research: Intima–media thickness appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Intima–media thickness in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Intima–media thickness is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cardiology, Cardiovascular diseases, Ultrasound, so understanding it makes those chapters shorter.
In everyday life: Look for Intima–media thickness outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Ask Teacher Smith questions about this articleOpens your AI tutor with a question about “Intima–media thickness” →

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Intima–media thickness in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Intima–media thickness means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Intima–media thickness out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Intima–media thickness in simple terms?

Why does Intima–media thickness matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Intima–media thickness?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Intima–media thickness.