The first clinical manifestation of cardiovascular disease often arises in a stage of well-advanced atherosclerosis. However, arterial vessel wall changes occur during a presumably long subclinical lag phase characterized by functional disturbances and by gradual thickening of intima-media. IMT of large peripheral arteries, especially carotid, can be assessed by B-mode ultrasound in a relatively simple way. The measurement of IMT has emerged as one of the methods of choice for determining early atherosclerotic changes, the anatomic extent of atherosclerosis and its progression.
A close relationship of IMT with a number of cardiovascular risk factors has been found. The carotid IMT was estimated to increase by 0,04mm for every 10 years of age. Furthermore, a carotid IMT is affected by lifestyle. In the Monitored Atherosclerosis Regression Study (MARS) (1) cholesterol intake, body mass index and smoking were significantly related to the annual progression of carotid IMT. We observed that an increase in carotid IMT is related to the duration and number of cigarettes smoked (2). The IMT measurement would be also useful in evaluation of new (non classical) risk factors such as the lipoprotein(a) level, hyperhomocysteinemia and markers of thrombotic risk. Of all the traditional risk factors, hypertension appears to have the greatest effect on IMT. In one of our studies (3) increased IMT was found in young normotensive subjects with hypertensive familiar trait, suggesting that increased thickness of arterial wall precedes the onset of hypertension and is probably directly inherited vessel wall abnormality.
Carotid IMT is a well-established measure for assessing the cardiovascular risk, the extent of atherosclerosis and end-organ damage. Carotid IMT has proved to be an independent risk factor for myocardial infarction and stroke. In a prospective study on 1257 men, the risk of acute myocardial infarction increased by 11% for each 0,1mm increase in IMT (4) and it was shown that the carotid IMT above 1mm was associated with two-fold greater risk of acute myocardial infarction over 3 years. Furtherlore, in the Cardiovascular Health Study (CHS) an increased IMT was associated with a four fold greater risk of combined acute myocardial infarction and stroke over 6 years (5). Therefore, increased carotid IMT is a mirror of atherosclerotic burden and predictor of subsequent events. Because of its quantitative value, carotid IMT measurement is more and more frequently used in clinical trials to follow the harmful effects of risk factors on vessel walls in individual patients and, more importantly, the effect of treating risk factors that cause reduction or prevent the progression of the IMT, paralleled by a decrease in cardiovascular risk and events. Therefore, IMT measurements may be used in addition to classical risk factors of individual risk assessment. More recently, there has been interest in the clinical use of this technique for detecting preclinical (asymptomatic) atherosclerosis and for identifying high risk subjects in primary prevention. Measurement of carotid IMT could influence a clinician to intervene with medication and to use more aggressive treatments of risk factors in primary prevention, and in patients with atherosclerotic disease in whom there is evidence of extension of atherosclerosis on carotid arteries.
The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.
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