Attenuation of Rate of Change in Carotid Intima-Media Thickness by Lipid-Modifying Drugs Impact on Clinical Outcomes

Measurements of carotid intima-media thickness (CIMT) are widely used in clinical research as a measure of atherosclerosis. Many randomized controlled trials (RCTs) have been performed using the rate of change in CIMT as the primary endpoint to study the efficacy of lipid-modifying therapies. The main advantage of using CIMT over the use of cardiovascular events as a primary endpoint is the greater efficiency and feasibility. The underlying assumption for the use of CIMT in trials is that the rate of change in CIMT achieved by a therapy reflects a change in the risk for cardiovascular events. We therefore set out to assess the evidence showing whether the rate of change in CIMT induced by lipid-lowering therapies has an impact on clinical outcomes, by reviewing the available evidence based on a search of the PubMed database. Solid evidence from observational studies shows that increased CIMT relates to an increase in cardiovascular risk. RCTs consistently demonstrate that the annual rate of change in CIMT is favourably affected by lipid-modifying therapies. One study investigating the relationship between the rate of change in CIMT and clinical events has been published and showed a positive relationship between these two outcomes. A published meta-analysis based on pooled CIMT data from statin trials has shown a positive relationship between attenuated rate of change in CIMT after statin therapy and clinical outcomes. However, methodological issues question the validity of the meta-analytical approach. The consistent agreement between results from CIMT trials and event trials on the effects of lipid-modifying therapies, however, clearly supports the presence of a relationship between changes in CIMT and clinical endpoints. Therefore, although direct evidence is scarce, the data overall on whether the attenuation of rate of change in CIMT by lipid-lowering therapies impact on clinical outcomes are supportive.