Low-flow mediated constriction: the yin to FMD’s yang?

Abstract

Given the prevalence of cardiovascular disease (CVD), early detection is crucial. Although traditional cardiovascular risk factors relate to future CVD, the predictive value of these risk factors can be relatively limited. Contemporary scientific attention has focused on alternative direct measures of arterial function. Based on the ability of the endothelium to acutely dilate in response to an increase in flow, ‘flow mediated dilation’ (FMD) was introduced approximately 20 years ago and is now an established non-invasive index of endothelial function predictive of future cardiovascular events. Recently, ‘low-flow mediated constriction’ (L-FMC) has been proposed as a complementary addition to FMD. The technique is based on the constrictor response to decreased flow and is claimed to improve the sensitivity and specificity of FMD. The aim of this review is to examine literature pertaining to this novel technique and to provide insight into the potential use of L-FMC in future research.

Keywords::

• cardiovascular prognosis
• cardiovascular risk
• composite end point
• endothelial function
• flow-mediated dilation
• low-flow-mediated constriction

Financial & competing interests disclosure

DHJ Thijssen receives funding from the E Dekker stipend (Netherlands Heart Foundation, 2009T064).

DJ Green receives research funding support from the National Heart Foundation of Australia and the Australian Research Council. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Low-flow-mediated constriction (L-FMC) is a novel technique proposed for use alongside, but not instead of flow-mediated dilation.

• Early mechanistic studies have suggested L-FMC is endothelium-dependent, and possibly mediated by the release of vasoconstrictors and/or inhibition of vasodilators. Further blockade studies are required to pin-point precise mechanisms in order to truly understand the clinical importance of L-FMC.

• Heterogeneity in L-FMC responses seem to be present between the brachial and radial arteries.

• Currently, no data are available to support the potential prognostic impact of L-FMC or the composite end point.

• Further research is necessary to answer fundamental methodological questions in order to formulate a standardized approach.

Notes