Biologically implausible carotid intima-media thickness measurement values: effects on rate of change over time

Carotid Intima-media Thickness Measurements: Relations with Atherosclerosis, Risk of Cardiovascular Disease and Application in Randomized Controlled Trials

Advances in the field of carotid ultrasound have been incremental, resulting in a steady decrease in measurement variability. Improvements in edge detection algorithms point toward increasing automation of CIMT measurements. The major advantage of CIMT is that it is completely noninvasive and can be repeated as often as required. It provides a continuous measure since all subjects have a measurable carotid wall. It is also relatively inexpensive to perform, and the technology is widely available. A graded relation between raising LDL cholesterol and increased CIMT is apparent. Increased CIMT has been shown consistently to relate the atherosclerotic abnormalities elsewhere in the arterial system. Moreover, increased CIMT predicts future vascular events in both populations from Caucasian ancestry and those from Asian ancestry. Furthermore, lipid‑lowering therapy has been shown to affect CIMT progression within 12–18 months in properly designed trials with results congruent with clinical events trials. In conclusion, when one wants to evaluate the effect of a pharmaceutical intervention that is to be expected to beneficially affect atherosclerosis progression and to reduce CV event risk, the use of CIMT measurements over time is a valid, suitable, and evidence‑based choice.

Carotid intima-media thickness studies: study design and data analysis

BACKGROUND

Carotid intima-media thickness (CIMT) measurements have been widely used as primary endpoint in studies into the effects of new interventions as alternative for cardiovascular morbidity and mortality. There are no accepted standards on the use of CIMT measurements in intervention studies and choices in the design and analysis of a CIMT study are generally based on experience and expert opinion. In the present review, we provide an overview of the current evidence on several aspects in the design and analysis of a CIMT study on the early effects of new interventions.

SUMMARY OF ISSUES

A balanced evaluation of the carotid segments, carotid walls, and image view to be used as CIMT study endpoint; the reading method (manual or semi-automated and continuously or in batch) to be employed, the required sample size, and the frequency of ultrasound examinations is provided. We also discuss the preferred methods to analyse longitudinal CIMT data and address the possible impact of, and methods to deal with missing and biologically implausible CIMT values.

CONCLUSIONS

Linear mixed effects models are the preferred way to analyse CIMT data and do appropriately handle missing and biologically implausible CIMT values. Furthermore, we recommend to use extensive CIMT designs that measure CIMT at regular points during the multiple carotid sites as such approach is likely to increase the success rates of CIMT intervention studies designed to evaluate the effects of new interventions on atherosclerotic burden.

Results From a Carotid Intima-Media Thickness Trial as a Decision Tool for Launching a Large-Scale Morbidity and Mortality Trial

Background—

Trials with carotid intima-media thickness (CIMT) as primary end point may improve the efficiency of the evaluation of new therapies targeting atherosclerosis considerably, and the results of CIMT trials may be used as a decision tool to help in the choice to launch or not to launch a large-scale morbidity and mortality (M&M) trial. We evaluated the literature to provide evidence to support or refute this proposition.

Methods and Results—

PubMed Medline was systematically searched on May 1, 2012, for randomized double-blind controlled CIMT trials. The agreement between the results from CIMT and M&M trials was assessed, and positive and negative predictive values were calculated. Forty-eight CIMT trials were included. CIMT trials (n=20) on lipid-level modifying therapies are all, except one, in agreement with the M&M trial findings. For blood pressure-lowering trials (n=13), 3 were not congruent with the M&M trial. The positive and negative predictive value (95% confidence interval) of a CIMT trial to predict the outcome of a M&M trial are 96% (80–99%) and 83% (64–93%), respectively. The predictive values are higher for lipid-level modifying therapies than for other therapies.

Conclusions—

A CIMT trial positioned before an M&M trial may considerably improve the efficiency of the evaluation of new drug therapies on atherosclerosis and cardiovascular disease risk. Hence, the results of a CIMT trial should be seen as a decision tool to support or refute the start of a large-scale M&M trial on drugs targeting atherosclerosis.