REGIONAL DIFFERENCES IN MECHANICAL-PROPERTIES BETWEEN MAJOR ARTERIES - AN EXPERIMENTAL-STUDY IN SHEEP

Purpose: To study possible differences in mechanical properties betwee n central (abdominal aorta) and more peripheral (common carotid and co mmon femoral) arteries validating an earlier non-invasive study in chi ldren showing that central arteries are more distensible than peripher al ones. As invasive blood pressure was needed, but ethically impossib le to obtain in children in an experimental setting, an animal model w as chosen. Design: Open experimental study. Setting: Animal laboratory at university hospital. Material and Methods: The pulsatile vessel wa ll movements of the abdominal aorta (AA), common femoral (CFA) and com mon carotid (CCA) artery of nine sheep were examined using an ultrasou nd phase-locked echo-tracking technique. Intra-arterial blood pressure teas measured and pressure-diameter relations, pressure strain elasti c modulus (Ep) and stiffness (beta) calculated. Distensibility was def ined as the inverse of Ep and stiffness. Results: The AA showed lower values for Ep and stiffness (beta) than the CFA (p = 0.002) and CCA (p = 0.006), i.e. the latter two vessels were stiffer. The pressure-diam eter relations confirmed these differences and showed a non-linearity for all three vessels with increased stiffness above 70-90 mnz Hg. Con clusion: This study on young animals supports earlier findings of diff erences in mechanical properties between central and more peripheral a rteries seen in healthy children. As pathologies between these vessels differ, with dilatation of the abdominal aorta and occlusive disease in the more peripheral vessels, part of the explanation might be found in the mechanical properties of the healthy vessels, characterised he re with the echo-tracking technique.