Vascular compliance versus flow-mediated vasodilation: correlation with cardiovascular risk factors

Cardiovascular risk factors are associated with impaired endothelium dependent vasodilation and reduced vascular compliance. In this study, the correlation with cardiovascular risk factor score of two common techniques for assessing vascular function was compared. Risk factors and vascular function were evaluated in a study population of 122 people with peripheral arterial disease (PAD) or with risk factors for PAD (73 men and 49 women; mean age 69 years). A risk factor score was determined using Framingham criteria. Vascular compliance was assessed by pulse waveform analysis and simultaneous blood pressure measurement. Flow-mediated vasodilation of the brachial artery was measured using duplex ultrasonography. Participants with a high risk factor score had significantly reduced vascular compliance of large and small vessels. By contrast, the difference in flow-mediated vasodilation between those with a high or low risk factor score did not reach statistical significance. There was a significant negative correlation between vascular compliance and risk factor score. There was a similar trend between flow-mediated vasodilation and risk factor score, but this did not reach statistical significance. A measure of vascular compliance was more significantly correlated with cardiovascular risk factor score than was a measure of flow-mediated vasodilation in the study population. Neither technique provided values that were highly correlated with risk factor burden. Although flow-mediated vasodilation is a preferred research tool for assessing vascular function, technical limitations and biological variability may reduce its clinical application in assessing individual cardiovascular risk.