Increased intima-media thickness (IMT) is a non-invasive marker of early arterial wall alteration, which is easily assessed in the carotid artery by B-mode ultrasound, and more and more widely used in clinical research. Methods of IMT measurement can be categorized by two approaches: (i) measurement at multiple extracranial carotid sites in near and far walls and (ii) computerized measurement restricted to the far wall of the distal common carotid artery. Because IMT reflects global cardiovascular risk, its normal value might be better defined in terms of increased risk rather than in terms of statistical distribution within a healthy population. The available epidemiological data indicate that increased IMT (at or above 1 mm) represents a risk of myocardial infarction and/or cerebrovascular disease. Close relationships have been shown between: (i) most traditional cardiovascular risk factors; (ii) certain emerging risk factors such as lipoproteins, psychosocial status, plasma viscosity, or hyperhomocysteinemia; and (iii) various cardiovascular or organ damages such as white matter lesion of the brain, left ventricular hypertrophy, microalbuminuria or decreased ankle to brachial systolic pressure index. Thus, IMT gives a comprehensive picture of the alterations caused by multiple risk factors over time on arterial walls. Prospective primary and secondary prevention studies have also shown that increased IMT is a powerful predictor of coronary and cerebrovascular complications (risk ratio from 2 to 6) with a higher predictive value when IMT is measured at multiple extracranial carotid sites than solely in the distal common carotid artery. Therapeutic double-blind trials have shown that lipid-lowering drugs, such as resin and overall statines, and to a lesser extent antihypertensive drugs, such as calcium antagonists, may have a beneficial effect on IMT progression in asymptomatic or in coronary patients. However, methodological standardization of IMT measurement still needs to be implemented before routine measurement of IMT can be proposed in clinical practice as a diagnostic tool for stratifying cardiovascular risk in primary prevention and for aggressive treatment decision. It can be anticipated however, that the presence of increased carotid IMT in one individual with intermediate cardiovascular risk would lead to his classification into the high-risk category and thus influence the aggressiveness of risk factor modifications.
Abstract-We reviewed prospective epidemiological data in the general population, mostly middle-aged to older persons, to determine the association of carotid intima-media thickness (CIMT) (assessed by B-mode ultrasonography) with cardiovascular risk. Reported risks were expressed as absolute (event risk per persons-years in subjects with a high CIMT) and relative (hazard ratio of high vs low CIMT). They were hardly comparable as the result of differences between the analyzed studies, including the site and procedure of CIMT measurement, the report of adjusted or unadjusted models, and the arbitrary cutoff point to evaluate the CIMT ability to predict risk. Despite these heterogeneities, the following four main conclusions emerged: (1) CIMT was an independent but relatively modest (as judged by absolute risk) predictor of coronary heart disease (CHD); (2) CIMT was an independent predictor for stroke, slightly better than for CHD as judged by the relative risks of both events; (3) CIMT added little to the CHD prediction by risk factors, as judged by c statistic and receiver operating characteristic curve analysis (however, appropriate data for stroke on this important issue were lacking); and (4) the CHD prediction by CIMT was inferior to that by ultrasonography-assessed carotid plaque because plaque may be more representative of atherosclerosis than CIMT. Key Words: carotid intima-media thickness Ⅲ stroke Ⅲ coronary heart disease risk Ⅲ ultrasonography T he widespread clinical application of B-mode ultrasonographic measurement of carotid intima-media thickness (CIMT) for stratifying cardiovascular risk in primary prevention is secondary to the epidemiological evidence that increased CIMT is a worthwhile predictor of subsequent coronary heart disease (CHD) and stroke, the two leading causes of cardiovascular death. 1 The present study attempts to provide an analysis of epidemiological data towards the value of CIMT for predicting CHD and stroke. Special attention is given to the added predictive value of these data, beyond traditional risk factors, and their comparative prognostic performance, vs more representative measures of atherosclerosis such as ultrasonographicassessed plaques.
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