Observations of time-based measures of flow-mediated dilation of forearm conduit arteries: implications for the accurate assessment of endothelial function.
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.
Liuni
Andrew
A
Division of Cardiology, Mount Sinai and University Health Network Hospitals, Canada.
Luca
Mary Clare
MC
Lisi
Monica
M
Dragoni
Saverio
S
di Stolfo
Giuseppe
G
Mariani
Justin A
JA
Uxa
Amar
A
Gori
Tommaso
T
Parker
John D
JD
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*
D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester