Wave intensity analysis in air-filled flexible vessels

Stiffening and ventricular-arterial interaction in the ascending aorta using MRI: ageing effects in healthy humans

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Objectives:

The aim of this study was to investigate the effect of age and sex on _nPWV and _ndI in the ascending aorta of healthy humans.

Background:

Local pulse wave velocity (_nPWV) and wave intensity (_ndI) in the human ascending aorta have not been studied adequately, because of the need for invasive pressure measurements. However, a recently developed technique made the noninvasive determination of _nPWV and _ndI possible using measurements of flow velocity and arterial diameter.

Methods:

Diameter and flow velocity were measured at the level of the ascending aorta in 144 healthy participants (aged 20–77 years, 66 men), using MRI. _nPWV, _ndI parameters; forward (FCW); backward (BCW) compression waves, forward decompression wave (FDW), local aortic distensibility (_nD_s) and reflection index (_nRI) were calculated.

Results:

_nPWV increased significantly with age from 4.7 ± 0.3 m/s for those 20–30 years to 6.4 ± 0.2 m/s for those 70–80 years (P < 0.001) and did not differ between sexes. _nD_s decreased with age (5.3 ± 0.5 vs. 2.6 ± 0.2 10⁻⁵ 1/Pa, P < 0.001) and _nRI increased with age (0.17 ± 0.03 vs. 0.39 ± 0.06, P < 0.01) for those 20–30 and 70–80 years, respectively. FCW, BCW and FDW decreased significantly with age by 86.3, 71.3 and 74.2%, respectively (P < 0.001), all compared to the lowest age-band.

Conclusion:

In healthy humans, ageing results in stiffer ascending aorta, with increase in _nPWV and decrease in _nD_s. A decrease in FCW and FDW indicates decline in left ventricular early and late systolic functions with age in healthy humans with no differences between sexes. _nRI is more sensitive than BCW in establishing the effects of ageing on reflected waves measured in the ascending aorta.