P163 Regional Differences in Geometrical Features and Layer-Specific Residual Stresses in the Bovine Descending Thoracic Aorta

Abstract

Background

The Opening Angle (OA) is widely used as an index of the residual stresses and strains present in the arterial wall not subjected to internal pressure. The aim of this work was to quantify regional variation of the layer-specific OA in the bovine descending thoracic aorta.

Methods

Descending thoracic aortae from 7 cows were segmented into 3–4 mm wide rings. Geometrical features (mean internal/external radius Rin and Rout, wall thickness h) were measured. A radial cut was made on the anterior region of each ring, and then the rings were placed in a temperature-controlled water bath (37 °C) for 1.5 h to express the OA. The rings were separated into their three layers and the layer-specific OA was investigated. The separation of the intima from the media is a complex procedure due to its limited thickness. The isolated intima was therefore thicker than values reported in the literature.

Results

Except for the most proximal region, h/Rin decreased towards the periphery (table 1). The medial and whole aortic wall OA increased moving towards the periphery, whilst the adventitia showed the opposite behaviour. The intimal OA was significantly higher and relatively constant (figure 1).

Conclusions

The present set of experiments indicates that the compressive residual stresses are concentrated mainly in the internal part of the intima-media layer independently from the considered axial region. The other layers exhibit comparable OAs to the whole arterial wall.