Frankfurt, Germany - Confirmation that carotid intima-media thickness (IMT) is a reliable predictor of future risk of cardiovascular events has come from a new meta-analysis [1]. The meta-analysis, published online January 22, 2007 in Circulation, found that carotid IMT is a strong predictor of both stroke and MI.

The authors, led by Dr Matthias Lorenz (Johann Wolfgang Goethe-University, Frankfurt, Germany), explain that as carotid IMT can be measured relatively simply and noninvasively, it is well-suited for use in large-scale population studies and it is increasingly being used for risk stratification in individuals and as an end point in intervention studies. But an important precondition for this application of IMT is that it can predict future risk of clinical vascular events. They note that a number of longitudinal studies have examined the relationship between IMT and future events, but different studies have used different measurement methods and studied different populations. Furthermore, some studies have investigated relatively small populations, which resulted in large confidence intervals for the risk estimates. To gain more robust estimates of the predictive value of increased IMT for clinical cardiovascular end points, they carried out a meta-analysis of these studies.

They reviewed data from eight studies, with a total of 37 197 subjects who were followed up for a mean of 5.5 years. Results showed that after adjustment for age and sex, increased carotid IMT was associated with increased risk of both MI and stroke.

"With data of 200 000 person-years in eight studies, the results of this meta-analysis improve the precision of estimating the risk that is associated with IMT," the researchers write. "For an absolute carotid IMT difference of 0.1 mm, the future risk of MI increases by 10% to 15% and the stroke risk increases by 13% to 18%," they report.

In an interview with heartwire, one of the authors, Dr Hugh Markus (St George's University of London, UK), said this study should increase confidence in carotid IMT as a measure of future risk of cardiovascular events. "With the large population included in this meta-analysis, we can be much more certain exactly how carotid IMT measurements relate to future risk. If you are going to use a marker as an end point in clinical trials, you have to have robust data on how it relates to risk, and now we have such data."

Markus said this study confirms that carotid IMT is a suitable end point for studies of potential new antiatherosclerotic drugs, and it can also be used to predict risk in health screening. "The carotid artery is simple to visualize with an ultrasound scan, as it is so close to the skin surface, so that a clear measurement of IMT can be seen very easily, and this study suggests that thickening of this artery wall by atherosclerosis is a good indicator of what is going on in the vasculature generally," he added.