Abdominal aortic aneurysm (AAA) is a pathological dilation of the abdominal aorta affecting ~1% of 65-year-old men in Sweden. AAA is usually asymptomatic until rupture, a catastrophic event with ~80% mortality. No medication currently halts or reverses AAA due to incomplete understanding of its underlying mechanisms. Evidence suggests that AAA may represent a focal manifestation of a systemic vascular disease, supported by observations of enlarged peripheral arteries and altered peripheral arterial regulation. However, whether elastic and muscular arteries are similarly affected remains unclear, and studies of peripheral arterial regulation, venous function, and their impact on overall haemodynamics in AAA are limited. Therefore, this thesis aimed to investigate arterial diameter and function in elastic and muscular arteries of the arm and neck, cardiovascular responses to hypovolemia-induced sympathetic activation, and venous function in individuals with AAA and controls.

Participants were recruited from a regional AAA screening program. The radial- (RA), distal brachial- (BAdist), proximal brachial- (BAprox), axillary- (AXA), and common carotid artery (CCA) were scanned using ultrasound. Arterial diameter, wall thickness, and arterial stiffness were assessed using manual and software-assisted methods. Venous occlusion plethysmography was used to assess forearm and calf venous compliance and capacitance, as well as forearm vascular resistance while sympathetic activation was induced using lower body negative pressure (LBNP).

We found that individuals with AAA exhibited larger and stiffer elastic arteries and similar arterial wall thickness across all arteries compared with controls. In response to increasing LBNP, individuals with AAA displayed blood pressure instability, impaired forearm vascular resistance, and reduced mobilisation of forearm venous blood. Forearm venous compliance was also lower in individuals with AAA compared with controls.

In summary, abdominal aortic aneurysm is associated with marked pathological alterations in elastic arteries, the venous system, and arterial regulation, strengthening the view of AAA being a focal manifestation of a systemic vascular disease.