Evaluation of the Role of Adventitia in Veins of Experimental Animals: Elastic and Viscous Analysis
The dynamic role of the adventitia layer has been largely studied on arteries, whereas less emphasis has been given to the mechanical properties of veins. The purpose of this research was to analyze the biomechanical properties of left jugular veins before and after adventitial removal in an ex-vivo animal model. In 14 experimental sheep under general anesthesia a 10-centimetre long segment was isolated. Ultrasonic crystals to measure instantaneous diameter and a pressure sensor were placed. Two tourniquets were positioned on both extremities of the vascular segment. Acute changes in intraluminal pressure were performed in each intact vessel segment, after temporarily isolating the vessel with the vascular tourniquets. This maneuver was repeated after removing the adventitia. The biomechanical analysis of the jugular veins using a third pole order model showed that mean values of vascular stiffness (elastic modulus) obtained after the removal of the adventitia were significantly higher than those observed in intact vessels (2.164 ± 1.530 mmHg.mm-1 versus 4.460 ± 3.247 mmHg.mm-1 respectively, p<0.05). However, no statistical differences were observed in terms of vascular viscosity, inertial index and cut-off frequency values. In this ex vivo animal model it was demonstrated that the removal of the adventitia increases the elastic modulus in veins subjected to intraluminal systemic pressure levels.