NEUROSONOLOGY
Intima-media thickness (IMT)
Created 26/03/2021, last revision 09/01/2023
- carotid intima-media thickness (IMT, CIMT) measurement can quantify atherosclerosis burden in asymptomatic patients, which may need a more aggressive approach to managing vascular risk factors
- the standard measurement is performed in B-mode on the far wall of the CCA, 10 mm proximal to the bifurcation
- use high-resolution images
- optimize the insonation angle (90° to the vessel wall)
- measure the distance between the 2 echogenic lines
- the 1st line is the lumen-intima interface
- the 2nd line is the media-adventitia interface
- obtain at least five measurements on each side and get an average value (“average IMT”); specialized software may be helpful
[Baldassare, 2000] - avoid atherosclerotic plaques when measuring IMT (lesions > 1.5 mm are already considered plaque)
- echogenicity, especially of the media, may be increased in the presence of fatty infiltration and thickening
- IMT > 95th. percentile for age and sex is considered abnormal (usually IMT >1 mm is abnormal)
| Female (95. percentile) |
Male (95. percentile) |
||||
|
45 y
|
55 y |
65 y |
45 y | 55 y |
65 y |
|
0.73
|
0.91 | 1.04 |
0.89
|
1 | 1.3 |
95.th percentile [Howard, 1993]
| Age |
P25 | P50 |
P75 |
|---|---|---|---|
| Men <30 | 0.39 | 0.43 | 0.48 |
| Men 31-40 | 0.42 | 0.46 | 0.50 |
| Men 41-50 | 0.46 | 0.50 | 0.57 |
| Men >50 | 0.46 | 0.52 | 0.62 |
| Women <30 | 0.39 | 0.40 | 0.43 |
| Women 31-40 | 0.42 | 0.45 | 0.49 |
| Women 41-50 | 0.44 | 0.48 | 0.53 |
| Women >50 | 0.50 | 0.54 | 0.59 |
Prognostic value of IMT measurement
- not only atherosclerotic plaques but also IMT can quantify atherosclerosis burden in asymptomatic patients
- IMT should be assessed in each extracranial ultrasound examination
- increased IMT is the first stage of atherosclerosis and, if left untreated, is followed by plaque formation
- clinical and epidemiological studies have shown an association between IMT and coronary artery disease (CAD), stroke, and peripheral vascular disease (PAD) (ROTTERDAM, ACAPS trials ) [Lorenz, 2007]
- thickening of IMT correlates with the presence of traditional vascular risk factors (BMI, hypertension, hypercholesterolemia, diabetes, smoking)
- some authors recommend including IMT and the presence of AS plaques among the classic vascular risk factors [Chambless, 2010]
- some publications question the importance of IMT in predicting CV events [Costanzo, 2010] [Ruijter, 2012]
- detection of subclinical atherosclerosis is important in patients with borderline risk and multiple risk factors, as it moves the patient into the high-risk category (SCORE ≥ 5%) with all therapeutic consequences
- pharmacological studies have shown a reduction in the rate of progression of IMT with hypolipidemic therapy and antihypertensive drugs (ACAPS, METEOR)
- rosuvastatin did not induce disease regression
- on the other hand, a meta-analysis of 41 randomized trials showed regression of cardiovascular events with hypolipidemic drugs but did not show a relationship between a decrease in CV events and a regression of IMT [Costanzo, 2010]
- an increase in IMT can also be found in non-atherosclerotic diseases (e.g., Takayasu´s arteritis)
