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

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.