Monday, December 23, 2013

Carotid artery intima media thickness (CIMT) is it a reliable marker of atherosclerosis?

In our county we do not measure the carotid artery intima media thickness in the routine clinical practice. But for the research trials this examination is done to know effect of drugs. This is a surrogate marker. There are doubts raised about the value of the CIMT measurement to know the CV risk. The CIMT may not give more information than that shown by traditional risk factors. A large number of prospective studies have demonstrated that carotid artery intima-medial wall thickening is predictive of major cardiovascular events, independently of traditional risk factors, with risk ratios ranging from 1.4 to 5.1 for coronary heart disease, and from 2.0 to 3.5 for stroke. Because of its established predictive value and its quantitative measurement with high precision and reproducibility rates, CIMT is also being employed as a surrogate endpoint in numerous clinical trials involving lipid-lowering or anti hypertensive drugs.
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Den Ruijter HM, Peters SA, Anderson TJ, et al. Common carotid intima-media thickness measurements in cardiovascular risk prediction: a meta-analysis. JAMA 2012;308:796—803.



Carotid artery plaque may be a better predictive marker than CIMT. Indeed, when measured in the common carotid artery usually free from atherosclerotic plaque, CIMT is not a specific marker of the atherosclerotic process, but it reflects  medial hypertrophy, particularly as a consequence of hypertension or ageing. Accordingly, polled data from several longitudinal studies showed that the absolute risk of coronary
heart disease at 10 years associated with the presence of carotid plaque was 25% compared with 8% (low risk) in the absence of plaque, contrasting with an absolute risk of 11 to 15% (still intermediate risk) in subjects with CIMT > 95th percentile. However, the current recommendation to measure CIMT in order to reclassify intermediate-risk subjects  is not supported by its actual predictive value, which suffers established weakness beyond traditional risk factors compared with that of carotid plaque and coronary artery calcinosis.
http://ac.els-cdn.com/S1875213613000089/1-s2.0-S1875213613000089-main.pdf?_tid=dc099cf4-6bb5-11e3-93f6-00000aacb35d&acdnat=1387791637_b577dba96c2e307acb0ede59976abd00
In another study published in Lancet it was concluded that - The association between cIMT progression assessed from two ultrasound scans and cardiovascular risk in the general population remains unproven. No conclusion can be derived for the use of cIMT progression as a surrogate in clinical trials.
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(12)60441-3/abstract

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