Changes in segmental arterial stiffness and volume dynamics across the arterial tree during noradrenaline...

Vascular function depends on arterial stiffness and volume dynamics; however, segmental differences remain unclear. Segmental arterial stiffness can be assessed using a cardio-ankle vascular index (CAVI)-based stiffness parameter (segmental-β), and volume changes can be estimated using intravascular ultrasound (IVUS). In this study, segmental-β and arterial caliber changes in the aorta and iliofemoral arteries were investigated during noradrenaline (NAD) administration with the aim of clarifying segmental vascular function and its interactions. Anesthetized rabbits received low, medium, and high NAD doses (10, 100, and 1000 μg/kg) and hemodynamic parameters were measured. The results showed that blood pressure and peripheral vascular resistance increased in a dose-dependent manner. IVUS demonstrated dose-dependent increases in arterial caliber in both the aorta and iliac arteries, as well as in estimated aortic volume. At low and medium NAD doses, iliac-β increased, whereas aortic-β decreased. In contrast, at the high NAD dose, iliac-β turned downward, and aortic-β turned upward. Despite uniform arterial dilation associated with volume centralization induced by peripheral arteriolar vasoconstriction, arterial stiffness exhibited reciprocal segmental changes. Overall, this intersegmental vascular response may be conceptualized as an "arterial ballooning chain effect" involving elastic arteries, muscular arteries, and arterioles under strong vasoconstrictive stress. This phenomenon might be an adaptation of central blood pooling among various arterial trees.