Variation in non-invasive measurements of vascular function in healthy volunteers during daytime

Abstract

Although it is often recommended to standardize the time of day when performing non-invasive measurements of vascular function, the exact influence of the time of day on the outcome of IMT (intima-media thickness), PWV (pulse wave velocity), AIX (augmentation index) and FMD (flow-mediated dilatation) measurements has not been reported before. Nineteen healthy volunteers visited our department on two different occasions: the first visit was at 09:00 hours after an overnight fast, and the second visit was at 14:00 hours after a standardized breakfast. Non-invasive measurements of atherosclerosis were performed twice at 09:00 hours and once on the second visit at 14:00 hours. Measurement of IMT, PWV, AIX and FMD was reproducible according to the method of Bland and Altman. The absolute difference between repeated measurements at 09:00 hours showed no significant difference compared with the absolute difference between 09:00 and 14:00 hours for IMT (0.029+/-0.014 compared with 0.021+/-0.014 mm; P = 0.27), PWV (0.63+/-0.50 compared with 0.75+/-0.74 m/s; P = 0.52), AIX (4.0+/-4.0 compared with 5.5+/-5.2%; P = 0.35) and FMD (3.8+/-3.7 compared with 4.2+/-2.9%; P = 0.70). In conclusion, our results show that, in healthy volunteers during the daytime, IMT, PWV, AIX and FMD outcomes are not confounded by variation in the exact time of the examination as long as other (exogenous) conditions, including food intake, smoking and intake of alcohol, are carefully controlled for.

Both flow-mediated vasodilation procedures and acute exercise improve endothelial function in obese young men

“…First, we cannot eliminate the possible diurnal variation in FMD in obese humans, although a diurnal variation seems of little importance for FMD (Etsuda et al 1999;ter Avest et al 2005). When a diurnal eVect on FMD has been shown Fig.…”

What is the role of non-invasive measurements of atherosclerosis in individual cardiovascular risk prediction?

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High-throughput ambulatory assessment of digital reactive hyperemia: Concurrent validity with known cardiovascular risk factors and potential confounding

“…We chose to include time of day in our analysis, but we cannot identify whether the significance of this variable is indicative of diurnal variation, serves as a proxy for temperature, or some combination of these effects (Etsuda et al, 1999). ter Avest et al (2005) found that diurnal variation in vascular function was insignificant if tests were performed during normal working hours under otherwise controlled conditions. No discernable pattern in the coefficient of variation for RHI, by time of day, was observed in our analysis.…”