title: Observations of time-based measures of flow-mediated dilation of forearm conduit arteries: implications for the accurate assessment of endothelial function.
abstract: Endothelium-dependent flow-mediated dilation (FMD) is measured as the increase in diameter of a conduit artery in response to reactive hyperemia, assessed either at a fixed time point [usually 60-s post-cuff deflation (FMD(60))] or as the maximal dilation during a 5-min continuous, ECG-gated, measurement (FMD(max-cont)). Preliminary evidence suggests that the time between reactive hyperemia and peak dilation (time to FMD(max)) may provide an additional index of endothelial health. We measured FMD(max-cont), FMD(60), and time to FMD(max) in 30 young healthy volunteers, 22 healthy middle-aged adults, 16 smokers, 23 patients with hypertension, 40 patients with coronary artery disease, and 22 patients with heart failure. As previously reported, FMD(max-cont) was similar in healthy cohorts and was significantly blunted in smokers and all patient groups, whereas FMD(60) was significantly blunted only in heart failure patients. There was a wide within-group variability between measures of time to FMD(max) with no significant difference between normal and patient groups. Intra-arterial infusion of the nitric oxide synthase inhibitor N(omega)-monomethyl-l-arginine in eight healthy subjects resulted in a blunting of FMD(max-cont) (P < 0.001) and FMD(60) (P = 0.02) but not time to FMD(max). Both FMD(max-cont) and FMD(60) demonstrated good repeatability in 30 young healthy volunteers studied on two separate occasions (P < 0.01 for both), whereas time to FMD(max) varied widely between visits (P = not significant). In conclusion, although time to FMD(max) does not appear to be a useful adjunctive measure of endothelial health, the use of continuous diameter measurements provides important data in the study of endothelial function in healthy subjects and patients with cardiovascular disease.
authors.affiliation: Division of Cardiology, Mount Sinai and University Health Network Hospitals, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Liuni
authors.forename: Mary Clare
authors.initials: MC
authors.lastname: Luca
authors.forename: Monica
authors.initials: M
authors.lastname: Lisi
authors.forename: Saverio
authors.initials: S
authors.lastname: Dragoni
authors.forename: Giuseppe
authors.initials: G
authors.lastname: di Stolfo
authors.forename: Justin A
authors.initials: JA
authors.lastname: Mariani
authors.forename: Amar
authors.initials: A
authors.lastname: Uxa
authors.forename: Tommaso
authors.initials: T
authors.lastname: Gori
authors.forename: John D
authors.initials: JD
authors.lastname: Parker
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001916:Brachial Artery / Q000187:drug effects / Q000503:physiopathology*; D003324:Coronary Artery Disease / Q000503:physiopathology*; D004730:Endothelium, Vascular / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012907:Smoking / Q000503:physiopathology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester