Flow-mediated vasodilatation: variation and interrelationships with plasma lipids and lipoproteins

Objective . Endothelial dysfunction is a critical, prerequisite step in atherosclerosis, and may be evaluated by flow-mediated vasodilatation (FMD). The objective of this study was to examine interrelationships between FMD and plasma lipids and lipoproteins, and to determine the between-operator and within-subject variability associated with this technique. Material and methods. FMD, plasma lipids and lipoproteins, including small dense LDL (sdLDL), were measured twice in 40 healthy volunteers, 4 weeks apart. Interrelationships between mean FMD responses and plasma lipids and lipoproteins were examined by correlation analysis. FMD measurements were taken by two independent operators, allowing determination of between-operator variability. Within-subject variability was determined by obtaining two measurements, 4 weeks apart, in every subject, and carried out by the same operator. Results. FMD was inversely related to plasma triglycerides (r=-0.47, p=0.002), total cholesterol/HDL cholesterol (r=-0.35, p=0.03) and apolipoprotein B (r=-0.36, p=0.02), but not to other plasma lipids and lipoproteins. When measuring variation in FMD, the following results were found: Between operators (SD=4.0 FMD%) and within subjects (SD=2.9 FMD%). Conclusions. The associations between FMD, plasma triglycerides and apoB provide evidence supporting a role for triglyceride-rich lipoproteins in endothelial dysfunction.