Arteries are continuously affected by pulsating blood flow resulting in a wall shear stress (WSS) load. WSS has been related both to the remodeling process in the arterial walls as well as atherosclerosis. These processes are both related to ageing.

10 young (23.5±1.4 years, BMI 21.8±1.4) and 8 old (58.0±2.8 years, BMI 24.0±2.3) subjects were studied. Computational fluid dynamics (CFD) together with magnetic resonance imaging (MRI) measurements were used to investigate the WSS in the healthy thoracic aorta (TA). MRI images (geometry and flow) were obtained and segmented to fit the CFD simulations. Time averaged WSS (TAWSS) and oscillating shear index (OSI) were extracted.

In young and old subjects, the diameter of the descending TA was 26±2.2 mm vs. 36±3.7 mm (p<0.001), and cardiac output (CO) 6.75±1.04 L/min vs. 4.17±0.90 L/min (p<0.001). In the whole TA, the TAWSS in the old was lower than in the young, while OSI only showed small differences. Fig 1a and b show reduced TAWSS with age in a cross-section of TA, and to some extent also in OSI.

Conclusions: WSS show distinct age-related changes with a major reduction in TAWSS, while OSI show only minor changes. This is associated with an increase in aortic diameter as well as decrease in CO. The distinct WSS-alterations could be a contributing factor both to the remodeling and atherosclerosis process over age.

Figure 1a

cross-section location.

Figure 1b

TAWSS and OSI distribution between the young and old subjects at a cross-section of the descending aorta (±SEM). Significance is indicated by ^* and ^** (p < 0.05 and p < 0.01, respectively).