Is the association between flow-mediated dilation and cardiovascular risk limited to low-risk populations?

OBJECTIVES The aim of this research was to study whether the relation between endothelial function measured by flow-mediated dilation (FMD) of the brachial artery and cardiovascular risk factors is affected by the baseline cardiovascular risk. BACKGROUND Flow-mediated dilation of the brachial artery is widely used as a measure of endothelial function. Relations between FMD and most cardiovascular risk factors have been described. METHODS We performed a meta-regression analysis of 211 selected articles (399 populations) reporting on FMD and cardiovascular risk factors. Mean values of FMD; age; proportion of men; proportion of smokers; blood pressure; lipids; glucose; and the presence of diabetes mellitus, of hyperlipidemia, and of hypertension were retrieved from the articles. The 10-year risk of coronary heart disease (CHD) for each population was estimated based on the Framingham risk score. The relation between FMD and cardiovascular risk factors was assessed within each risk category by linear regression analysis, adjusting for age and gender, and weighted for the study size. RESULTS A relation between FMD and cardiovascular risk factors was most clear in the category with lowest baseline risk (below 2.8 % per decade). In populations with low baseline risk, for each % increase in Framingham risk, FMD decreased by 1.42 % (95 % confidence interval: 0.65 to 2.19). In medium- and high-risk populations, FMD was not related to risk (-0.02 % [-0.27 to 0.22] and 0.06 % [-0.02 to 0.13], respectively). These findings were independent of differences in brachial lumen diameter and technical aspects of the FMD measurement. CONCLUSIONS Only in populations at low risk, endothelial function measured by FMD is related to the principal cardiovascular risk factors, and to the estimated 10-year risk of CHD. (c) 2005 by the American College of CardiologyFoundation.