We performed this study to evaluate the lower limit of the normal endothelial function, which can differentiate normal values from abnormal ones and to evaluate the changes of the endothelial function according to ages.

Study populations were consisted of four groups: patients (group A) with coronary artery disease (CAD) (n=2, mean age: 55 yrs), patients (group B) with one or more risk factors of atherosclerosis (n=3, mean age: 54 yrs), age- and sex-matched healthy subjects (group C, n=5, mean age: 54 yrs), and healthy young subjects (group D, n=3, mean age: 26 yrs). We measured the flow-mediated endothelium-dependent dilation (FMD) of brachial artery using a high-resolution ultrasound in all subjects. We analyzed the receiver operating characteristic (ROC) curve.

The FMD of the A and B group were significantly lowered (8.6±3.7% vs 9.9±4/5% than C (14.3±3.3%, p<0.001) or D group (18.0±3.5%, p<0.001). The FMD level of 11.5% had 76.3% of sensitivity and 76% of specificity to differentiate normal endothelial function from abnormal one. The spearman correlation coefficient between ages and FMD in groups C and D was -0.543 (p<0.001).

The endothelial function was decreased in patients with CAD or risk factors of atherosclerosis. We observed the age-related declining tendency of endothelial function in healthy subjects. 11.5% FMD) may be used to identify the person at risk of atherosclerosis.