Ultrasound Assessment of Brachial Artery Reactivity

Abstract

Conventional cardiovascular risk factors do not always provide sufficiently accurate estimates of cardiovascular risk. Detection of arterial abnormalities that antedate clinical cardiovascular disease could potentially help refine cardiovascular risk assessment. Brachial artery reactivity testing (BART) is a noninvasive modality to detect endothelial dysfunction, an early feature of atherogenesis. An increase in brachial artery blood flow is brought about through transient forearm occlusion, and high-resolution ultrasonography is used to measure the resulting flow-mediated dilatation (FMD) of the brachial artery, a vascular response that is believed to result at least in part from the hyperemia-induced release of nitric oxide from the endothelium in the upstream conduit artery. FMD is impaired in asymptomatic subjects with cardiovascular risk factors as well as in subjects with known cardiovascular disease. Several studies have shown impaired FMD to be associated with increased incidence of adverse cardiovascular events in select high-risk populations. Recent studies have also shown FMD to be predictive of future cardiovascular events in asymptomatic individuals. Furthermore, because endothelial dysfunction is involved in the development of atherosclerosis and its sequelae, FMD could be used as an intermediate endpoint to monitor risk-reduction therapy. BART may also be used to assess forearm microcirculatory function that has been recently shown to provide insights into pathophysiology of cardiovascular disease and to correlate with cardiovascular risk factor burden. Thus, BART appears to be a promising adjunct in cardiovascular risk assessment. However, there is need to have more data about the incremental prognostic value of FMD in asymptomatic individuals and to establish its usefulness in treatment monitoring. There is also a need to establish consensus risk-defining cut-off values of FMD.Key wordsArterial ultrasonographyBrachial artery reactivityCardiovascular riskEndothelial dysfunctionFlow-mediated dilatation