Background: Artery wall ageing involves elastic fibre loss and increased fibrosis, leading to dilatation and increased artery wall stiffness. Notably, the associated gradual transfer of tensile stresses from elastic to stiffer components in the wall will likely increase non-linear elastic behaviour of the vessel wall. We investigated whether age is indeed a determinant of carotid artery cross-sectional area (CSA) and stiffness non-linearity; the latter being quantified as the difference between systolic and diastolic pulse wave velocity: ΔPWV, in m/s (Figure).

Methods and Results: In 29 patients (21m/8f), carotid artery blood pressure and CSA waveforms were obtained by catheter and ultrasound. Diastolic, systolic and dicrotic notch amplitudes were determined for each individual (Figure). In 15 older patients (77±5yrs) compared to 14 younger (59±7yrs) carotid ΔPWV and CSA were increased (+2.6m/s and +7mm², resp., p<0.03), despite similar blood pressures. Moreover, in multiple regression analyses, age was a determinant of both ΔPWV and CSA, independent of sex, height and pulse pressure (p<0.01).

Older patients have a more non-linear preessure-area curve, at a greater cross-sectional area. Tags shows age and ΔPWV of the subjects. S denotes systolic; d, diastolic; dn, dicrotic notch. (Only a sample of 29 is shown for clarity.) PWV values are calculating using Bramwel-Hill: PWV=sqrt(1/rho* distensibility).

Conclusions: Our study demonstrates detectable age-related differences in carotid stiffness non-linearity and cross-sectional area, suggesting these may act as markers of vascular ageing.