EFFECTS OF AGING PER SE ON ARTERIAL STIFFNESS - SYSTEMIC AND REGIONALCOMPLIANCE IN BEAGLES

Although previous studies have suggested that aging results in an incr ease in vascular stiffness, diseases that increase in prevalence with advanced age may have confounded the results of some of this past rese arch. The purpose of this investigation was to determine whether aging per se results in reduced arterial compliance by using animals that a re resistant to atherosclerosis and do not develop hypertension or hyp erlipidemias with advanced age. We evaluated systemic and regional (fe moral) arterial compliance in older (110 +/- 8 months old) and in youn ger (27 +/- 2 months old) female beagle dogs by using a computer-based assessment of the diastolic decay of arterial pressure waveforms and a modified Windkessel model of the circulation. Although systemic arte rial pressure was very similar in both age groups, cardiac output was 29% lower (p = 0.03) and systemic vascular resistance was 24% higher ( p = 0.02) in the older dogs. Moreover, there was an age-related reduct ion in systemic arterial compliance, derived both from the exponential decay in the arterial pulse (C-1) (p = 0.05) and that derived from th e oscillatory component of the diastolic pulse wave (C-2) (P = 0.04). By contrast, although femoral vascular resistance was 25% higher in th e older dogs (p = 0.04), regional (femoral) vascular compliance measur ed after femoral arterial occlusion was also 25% reduced but was not s ignificantly changed with age (p = 0.14). These results demonstrate th at systemic arterial compliance is reduced with age in dogs, extending this finding to animals without age-related diseases that frequently occur in older human beings. Regional compliance, evaluated in the iso lated femoral vascular bed, also tends to be reduced with age, but var iability in this parameter in dogs reduces the significance of this fi nding.