Prediction of Clinical Cardiovascular Events With Carotid Intima-Media Thickness: A Systematic Review and Meta-Analysis
Background-Carotid intima-media thickness (IMT) is increasingly used as a surrogate marker for atherosclerosis. Its use relies on its ability to predict future clinical cardiovascular end points. We performed a systematic review and meta-analysis of data to examine this association. Methods and Results-Using a prespecified search strategy, we identified 8 relevant studies and compared study design, measurement protocols, and reported data. We identified sources of heterogeneity between studies.
... ty between studies. The assumption of a linear relationship between IMT and risk was challenged by use of a graphical technique. To obtain a pooled estimate of the relative risk per IMT difference, we performed a meta-analysis based on random effects models. The age-and sex-adjusted overall estimates of the relative risk of myocardial infarction were 1.26 (95% CI, 1.21 to 1.30) per 1-standard deviation common carotid artery IMT difference and 1.15 (95% CI, 1.12 to 1.17) per 0.10-mm common carotid artery IMT difference. The age-and sex-adjusted relative risks of stroke were 1.32 (95% CI, 1.27 to 1.38) per 1-standard deviation common carotid artery IMT difference and 1.18 (95% CI, 1.16 to 1.21) per 0.10-mm common carotid artery IMT difference. Major sources of heterogeneity were age distribution, carotid segment definition, and IMT measurement protocol. The relationship between IMT and risk was nonlinear, but the linear models fitted relatively well for moderate to high IMT values. Conclusions-Carotid IMT is a strong predictor of future vascular events. The relative risk per IMT difference is slightly higher for the end point stroke than for myocardial infarction. In future IMT studies, ultrasound protocols should be aligned with published studies. Data for younger individuals are limited and more studies are required. (Circulation. 2007;115:459-467.) Key Words: atherosclerosis Ⅲ carotid arteries Ⅲ meta-analysis Ⅲ myocardial infarction Ⅲ stroke C arotid intima-media thickness (IMT) is an intermediate phenotype for early atherosclerosis. Because it can be measured relatively simply and noninvasively, it is well suited for use in large-scale population studies. Ultrasonic measurements correlate well with histology, 1 and increased IMT is associated with vascular risk factors 2-12 and the presence of more advanced atherosclerosis, which includes coronary artery disease.     7, 10, 12 IMT is being increasingly used for risk stratification in individuals and as an end point in intervention studies. An important precondition for this application of IMT is that it can predict future risk of clinical vascular events. A number of longitudinal studies have examined the relationship between IMT and future events, most frequently the incidence of cardiac events (myocardial infarction [MI], angina pectoris, coronary intervention) and cerebrovascular events (stroke or transient ischemic attack [TIA]).            Clinical Perspective p 467 Different longitudinal studies have used different measurement methods and studied different populations. Furthermore, some studies have investigated relatively small populations, which resulted in large confidence intervals (CIs) for the risk estimates. We carried out a systematic review of the literature to provide an overview of the relevant studies, critically appraise the methods used, and where possible perform a meta-analysis to gain more robust estimates of the predictive value of increased IMT for clinical cardiovascular end points.