Limits...
Change of direction in the biomechanics of atherosclerosis.

Mohamied Y, Rowland EM, Bailey EL, Sherwin SJ, Schwartz MA, Weinberg PD - Ann Biomed Eng (2014)

Bottom Line: Lesion prevalence correlated positively, strongly and significantly with transWSS at both ages.Correlations of lesion prevalence with the other shear metrics were not significant or were significantly lower than those obtained for transWSS.The finding that oscillatory flow has pro-inflammatory effects when acting perpendicularly to the long axis of EC but anti-inflammatory effects when acting parallel to it may explain the stronger correlation of lesion prevalence with transWSS than with the OSI.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.

ABSTRACT
The non-uniform distribution of atherosclerosis within the arterial system has been attributed to pro-atherogenic influences of low, oscillatory haemodynamic wall shear stress (WSS) on endothelial cells (EC). This theory is challenged by the changes in lesion location that occur with age in human and rabbit aortas. Furthermore, a number of point-wise comparisons of lesion prevalence and WSS have failed to support it. Here we investigate the hypothesis that multidirectional flow-characterized as the average magnitude of WSS components acting transversely to the mean vector (transWSS)-plays a key role. Maps of lesion prevalence around aortic branch ostia in immature and mature rabbits were compared with equivalent maps of time average WSS, the OSI (an index characterizing oscillatory flow) and transWSS, obtained from computational simulations; Spearman's rank correlation coefficients were calculated for aggregated data and 95% confidence intervals were obtained by bootstrapping methods. Lesion prevalence correlated positively, strongly and significantly with transWSS at both ages. Correlations of lesion prevalence with the other shear metrics were not significant or were significantly lower than those obtained for transWSS. No correlation supported the low, oscillatory WSS theory. The data are consistent with the view that multidirectional near-wall flow is highly pro-atherogenic. Effects of multidirectional flow on EC, and methods for investigating them, are reviewed. The finding that oscillatory flow has pro-inflammatory effects when acting perpendicularly to the long axis of EC but anti-inflammatory effects when acting parallel to it may explain the stronger correlation of lesion prevalence with transWSS than with the OSI.

Show MeSH

Related in: MedlinePlus

The maps shown in Fig. 2 but with absolute values replaced by the rank order of pixels (blue = lowest pixel intensity, red = highest pixel intensity)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4286626&req=5

Fig3: The maps shown in Fig. 2 but with absolute values replaced by the rank order of pixels (blue = lowest pixel intensity, red = highest pixel intensity)

Mentions: Average maps of lesion prevalence and WSS metrics for immature and mature animals are shown in Fig. 2. The same maps are presented in Fig. 3 but absolute lesion frequencies and absolute values of WSS metrics have been replaced by ranks—that is, the pixel with the lowest intensity was given a rank of 1, the next lowest a rank of 2, etc.—to correspond with the ranking method used to calculate correlations between the maps.Figure 2


Change of direction in the biomechanics of atherosclerosis.

Mohamied Y, Rowland EM, Bailey EL, Sherwin SJ, Schwartz MA, Weinberg PD - Ann Biomed Eng (2014)

The maps shown in Fig. 2 but with absolute values replaced by the rank order of pixels (blue = lowest pixel intensity, red = highest pixel intensity)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4286626&req=5

Fig3: The maps shown in Fig. 2 but with absolute values replaced by the rank order of pixels (blue = lowest pixel intensity, red = highest pixel intensity)
Mentions: Average maps of lesion prevalence and WSS metrics for immature and mature animals are shown in Fig. 2. The same maps are presented in Fig. 3 but absolute lesion frequencies and absolute values of WSS metrics have been replaced by ranks—that is, the pixel with the lowest intensity was given a rank of 1, the next lowest a rank of 2, etc.—to correspond with the ranking method used to calculate correlations between the maps.Figure 2

Bottom Line: Lesion prevalence correlated positively, strongly and significantly with transWSS at both ages.Correlations of lesion prevalence with the other shear metrics were not significant or were significantly lower than those obtained for transWSS.The finding that oscillatory flow has pro-inflammatory effects when acting perpendicularly to the long axis of EC but anti-inflammatory effects when acting parallel to it may explain the stronger correlation of lesion prevalence with transWSS than with the OSI.

View Article: PubMed Central - PubMed

Affiliation: Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.

ABSTRACT
The non-uniform distribution of atherosclerosis within the arterial system has been attributed to pro-atherogenic influences of low, oscillatory haemodynamic wall shear stress (WSS) on endothelial cells (EC). This theory is challenged by the changes in lesion location that occur with age in human and rabbit aortas. Furthermore, a number of point-wise comparisons of lesion prevalence and WSS have failed to support it. Here we investigate the hypothesis that multidirectional flow-characterized as the average magnitude of WSS components acting transversely to the mean vector (transWSS)-plays a key role. Maps of lesion prevalence around aortic branch ostia in immature and mature rabbits were compared with equivalent maps of time average WSS, the OSI (an index characterizing oscillatory flow) and transWSS, obtained from computational simulations; Spearman's rank correlation coefficients were calculated for aggregated data and 95% confidence intervals were obtained by bootstrapping methods. Lesion prevalence correlated positively, strongly and significantly with transWSS at both ages. Correlations of lesion prevalence with the other shear metrics were not significant or were significantly lower than those obtained for transWSS. No correlation supported the low, oscillatory WSS theory. The data are consistent with the view that multidirectional near-wall flow is highly pro-atherogenic. Effects of multidirectional flow on EC, and methods for investigating them, are reviewed. The finding that oscillatory flow has pro-inflammatory effects when acting perpendicularly to the long axis of EC but anti-inflammatory effects when acting parallel to it may explain the stronger correlation of lesion prevalence with transWSS than with the OSI.

Show MeSH
Related in: MedlinePlus