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Shear rate normalization is not essential for removing the dependency of flow-mediated dilation on baseline artery diameter: past research revisited

2014; IOP Publishing; Volume: 35; Issue: 9 Linguagem: Inglês

10.1088/0967-3334/35/9/1825

1361-6579

Greg Atkinson,

Cerebrovascular and Carotid Artery Diseases

Normalisation of percentage flow-mediated dilation (FMD%) by shear rate (SR) was originally proposed to account for variability in the FMD% stimulus and in resting artery diameter (Dbase).It was not known at that time that FMD%-Dbase dependency is caused by the poor allometric properties of FMD% itself.Therefore, data from a seminal study on FMD%/SR normalisation were extracted and re-analysed.The absolute change in arterial diameter was found to be strongly inversely proportional to Dbase (r= -0.7, P<0.0005) and the allometric exponent was 0.82 (95%CI: 0.78-0.86),rendering use of FMD% inappropriate.Allometric scaling eliminated the originally-reported Dbase-dependency without any need for SR normalisation (r=0.0,P=0.96).The SR-FMD% correlation reduced from 0.69 to 0.37, following Dbase-adjustment.This reanalysis indicates that allometric scaling (i) renders FMD%/SR normalisation redundant for removing Dbase-dependency, and (ii) allows the influence of SR on the flow-mediated response to be quantified without the confounding influence of Dbase.