A pilot study with flow mediated skin fluorescence: A novel device to assess microvascular endothelial function in coronary artery disease

Background: Endothelial dysfunction is one of the earliest vascular manifestations in the pathogen­esis of cardiovascular disease. Noninvasive, simple, and inexpensive methods of endothelial function assessment are therefore needed. Methods: Microvascular endothelial function was assessed in coronary artery disease (CAD) patients by flow mediated skin fluorescence (FMSF), based on measurements of reduced form of nicotinamide adenine dinucleotide (NADH) fluorescence intensity during brachial artery occlusion (ischemic re­sponse [IRmax]) and immediately after occlusion (hyperemic response [HRmax]). Additionally, plasma levels of asymmetric dimethylarginine (ADMA) and endothelin-1 (ET-1) were measured to assess the association between biochemical markers and microvascular function evaluated in vivo by FMSF. Results: A significant inverse correlation was found between ADMA levels and hyperemic response (r = –0.534, p = 0.003), while ET-1 levels were inversely related to the ischemic response (r= –0.575, p = 0.001). Both IR and HR were found lowest in patients with advanced CAD and diabetes. When the repeatability of the method was tested, the intraclass correlation coefficient for IRmax and HRmax were 0.985 (p < 0.001) and 0.914 (p < 0.001), respectively. Moreover, in Bland and Altman analysis, both variables IRmax and HRmax showed good agreement in repeated measurements. Conclusions: In this pilot study, it was demonstrated that NADH fluorescence measured by FMSF device in CAD patients was associated with established plasma endothelial markers, and that both ischemic and hyperemic response were blunted in patients with advanced disease and diabetes. Fur­thermore, FMSF device showed excellent repeatability and good agreement for repeated measurements. However, further study is warranted to confirm these results in a larger patient cohort. (Cardiol J 2018; 25, 1: 120–127