Impact of thoracic endovascular aortic repair on radial strain in an ex vivo porcine model

Abstract

Objectives: To quantify the impact of thoracic endovascular aortic repair (TEVAR) on radial aortic strain with the aim of elucidating stent-graft-induced stiffening and complications.

Methods: Twenty fresh thoracic porcine aortas were connected to a mock circulatory loop driven by a centrifugal flow pump. A high-definition camera captured diameters at five different pressure levels (100, 120, 140, 160, and 180 mmHg), before and after TEVAR. Three oversizing groups were created: 0-9% ( n = 7), 10-19% ( n = 6), and 20-29% ( n = 6). Radial strain (or deformation) derived from diameter amplitude divided by baseline diameter at 100 mmHg. Uniaxial tensile testing evaluated Young's moduli of the specimens.

Results: Radial strain was reduced after TEVAR within the stented segment by 49.4 ± 24.0% ( P < 0.001). As result, a strain mismatch was observed between the stented segment and the proximal non-stented segment (7.0 ± 2.5% vs 11.8 ± 3.9%, P < 0.001), whereas the distal non-stented segment was unaffected ( P = 0.99). Stent-graft oversizing did not significantly affect the amount of strain reduction ( P = 0.30). Tensile testing showed that the thoracic aortas tended to be more elastic proximally than distally ( P = 0.11).

Conclusions: TEVAR stiffened the thoracic aorta by 2-fold. Such segmental stiffening may diminish the Windkessel function considerably and might be associated with TEVAR-related complications, including stent-graft-induced dissection and aneurysmal dilatation. These data may have implications for future stent-graft design, in particular for TEVAR of the highly compliant proximal thoracic aorta.

Keywords: Aortic strain; Stent-graft; TEVAR; Thoracic aorta; Uniaxial tensile testing.