Different Effects of Ageing on Elastic and Muscular Arterial Bifurcations in Men

In a previous study we have shown that the wall of the elastic carotid artery bifurcation (CAB) stiffens inhomogeneously with increasing age, the carotid artery bulb being most affected. In the present study the effect of ageing on the elastic properties of the wall and the strain the wall is exposed to along the muscular femoral artery bifurcation (FAB) was investigated using the CAB for comparison. The study was performed with 10 young (aged 20-30 years) and 10 old (50-60 years) presumed healthy volunteers. Distensibility along the bifurcation was determined by measuring noninvasively the maximum relative diameter changes of the artery during systole (peak delta d/d.100%), which is also a measure of strain, at various sites along both bifurcations by means of a vessel wall moving detector system. This system also makes the assessment of (end-diastolic) diameter possible. At all levels along the CAB, the diameter was significantly larger in the old than in the young. In the FAB, the diameter was only significantly larger in the old than in the young in the common and superficial femoral arteries. At all levels in the CAB, peak delta d/d.100% was significantly lower in the old than in the young, the carotid artery bulb being more affected than the common carotid artery (CCA), while in the FAB this parameter was lower in the old than in the young only in the common femoral artery (CFA). Peak delta d/d.100% was similar in the CCA and in the bulb in the young, but significantly higher in the CCA than at all levels in the bulb in the old. In the FAB, in the young peak delta d/d 100% was significantly higher in the CFA than at both levels in the deep and superficial femoral arteries, while in the old no significant differences in peak delta d/d.100% along the FAB could be detected. These findings indicate that the loss of wall elasticity with increasing age is different in the muscular and elastic arterial bifurcations investigated. The homogeneous distribution of wall elasticity in the elastic CAB at a younger age becomes inhomogeneous at an older age, while the opposite is observed in the muscular FAB. The changes in strain the different parts of the bifurcations are exposed to with increasing age are different in the CAB and the FAB. Differences in distensibility along bifurcations will make them deform inhomogeneously during the cardiac cycle.