Addition of Carotid Artery Wall Thickness to Risk Model Associated With Small Improvement in Prediction of Heart Attack, Stroke



In an analysis of data from previously published studies that included more than 45,000 patients, the value of adding to the Framingham Risk Score a measure of the common carotid artery intima-media thickness (CIMT; a measurement of the thickness of the carotid artery wall) in 10-year risk prediction of first-time heart attack or stroke was small and unlikely to be of clinical importance, according to an article in the August 22/29 issue of JAMA.

“Cardiovascular disease is among the leading causes of morbidity and mortality worldwide. Preventive treatment of high-risk asymptomatic individuals depends on accurate prediction of a person's risk to develop a cardiovascular event. Currently, cardiovascular risk prediction in asymptomatic individuals is based on the level of cardiovascular risk factors incorporated in scoring equations. Several scores are available, with the Framingham Risk Score (FRS) among the most widely used. These risk equations perform reasonably well, yet there remains considerable overlap in estimated risk between those who are affected by a cardiovascular event and those who are not,” according to background information in the article.

Measurement of CIMT has been proposed to be added to cardiovascular risk factors to improve individual risk assessment. “So far, individual studies reported on the added value of CIMT measurements in cardiovascular risk prediction, but the evidence is not consistent across studies,” the authors write.

Hester M. Den Ruijter, Ph.D., of the University Medical Center Utrecht, the Netherlands, and colleagues conducted a meta-analysis to determine whether common CIMT has added value in 10-year risk prediction of first-time heart attacks or strokes, above that of the Framingham Risk Score. The authors searched the medical literature and identified relevant studies for inclusion in the analysis. Studies were included if participants were drawn from the general population, common CIMT was measured at baseline, and individuals were followed up for first-time heart attack or stroke.

This analysis included 14 studies contributing data for 45,828 individuals. During a median (midpoint) follow-up of 11 years, 4,007 first-time heart attacks or strokes occurred. The researchers refitted the risk factors of the Framingham Risk Score and then extended the model with common CIMT measurements to estimate the absolute 10-year risks to develop a first-time heart attack or stroke in both models. More than 90 percent of the individuals remained in the same risk category. The numbers of individuals shifting downward or upward without and with events were similar. The net reclassification improvement with the addition of common CIMT was small (0.8 percent were correctly reclassified). In those at intermediate risk, the net reclassification improvement was 3.6 percent in all individuals, with no differences between men and women.

“Our results suggest that common CIMT measurements should not routinely be performed in the general population, as the overall added value may be too limited to result in health benefits,” the authors write. “However, as the interest in risk prediction is currently shifting from a 10-year risk to lifetime risk, the added value of a CIMT measurement and its cost-effectiveness using a horizon of 20 to 30 years may be worthwhile to explore.”

(JAMA. 2012;308[8]:796-803.