1345126 - CMR based quantification of age and sex-specific vessel wall characteristics of the ascending and abdominal aorta.

The ascending and abdominal aorta are regions at risk for aneurysms and rupture. Pulse wave velocity (PWV), vessel wall thickness (VWT) and wall shear stress (WSS) are CMR derived parameters (in)directly capable of characterising the vessel wall. The aim of this study was to investigate whether there are age and sex-specific differences in normal vessel wall characteristics assessed by CMR.

Methods:

94 healthy volunteers (48% male) equally distributed in five age groups (1: 18-29, 2: 30-39, 3: 40-49, 4: 50-59, 5: 60-70 years) were included in this study and underwent CMR imaging of the entire aorta. Semi-automatic segmentation of aortic volume in peak systolic phase was performed on 4D flow MRI. Seven planes were positioned perpendicular to the segmentation centerline, dividing the aorta into 7 segments (Figure 1). Axial (WSS_axial) and circumferential (WSS_circ) WSS were determined in the ascending and abdominal aorta (segments 2 and 7, respectively). VWT was determined in the ascending aorta at the level of the pulmonary trunk (VWT_asc) and proximal to the aortic bifurcation (VWT_abd) on two 2D black-blood dual-inversion recovery MRI acquisitions. PWV was assessed from 2D phase contrast MRI with the seven acquisition planes as shown in Figure 1. A weighted average was calculated in het ascending and abdominal aorta: PWV_asc and PWV_abd (segments 1-3 and 6-7, respectively).

Results:

Age and sex specific results of PWV, VWT and WSS are shown as boxplots in Figures 2 and 3. PWV_asc and PWV_abd increase with age, with significant differences between age groups (both p < 0.01), but not between sexes. Post-hoc analysis demonstrated that PWV_asc in age group 5 was significantly higher compared to all other groups (p < 0.01), and that PWV_abd had significant differences between all age groups, except 1 compared to 2, and 3 compared to 4. VWT_asc and VWT_abd increase by age, with significant differences between age groups (both p < 0.01) and also between sexes in VWT_asc (p < 0.05). Post-hoc analysis demonstrated higher values in women compared to men in age group 4 (p < 0.05), and VWT_asc in age groups 4 and 5 was significantly higher than in age groups 1-3 (p < 0.01). WSS_axial and WSS_circ decrease by age, with significant differences between age groups (both p < 0.01). Post-hoc analysis demonstrated that WSS_axial was significantly lower in age group 5 compared to age groups 1-3 in het ascending aorta (p < 0.01), and significantly lower in age groups 4 and 5 compared to age groups 1-3 in het abdominal aorta (p < 0.01). WSS_circ only showed significant differences in the abdominal aorta between age group 5 compared to age group 1 (p < 0.01) and age group 2 (p < 0.05).

Conclusion:

Significant differences between age groups and also between sexes emphasize the need of age and sex-specific normal values of vessel wall characteristics assessed by CMR of the ascending and abdominal aorta.