Residual Stent Graft Expansion Capacity in Frozen Elephant Trunk in Aortic Dissection: A Parameter to Evaluate the Counteracting between SG and the True Lumen

Objectives: In aortic dissection (AD) sizing of frozen elephant trunk (FET) is performed based on true lumen (TL) diameters to exclude entries and to expand the TL in the descending aorta. Thereby, the elliptical shape of the TL, in a static computed tomography (CT) imaging, complicates the diameter estimation. Stent graft (SG) expansion depends on the graduation of oversizing, SG radial force, stiffness of the aortic wall, and pressure in the false lumen. The aim of the study was to evaluate the impact of an incomplete unfolded SG at the distal landing zone after FET.

Methods: We retrospectively analyzed 149/259 patients with AD (105 acute, 44 chronic) after FET surgery in our institution between 01/2005 and 04/2019. Inclusion criteria was availability of repetitive CT scans ≥1 year (mean follow-up: 3.8 ± 2.7 years) in the absence of additional intervention downstream. Using 3D multiplanar reconstruction, the aortic lumen and TL diameters (mm) as well as areas (cm²) were evaluated. The TL area, with the expanded SG in place, defined the achieved graft deployment (TL-SG, cm²). Since a fabricated SG has a predefined lumen and area (f-SG area, cm²) the difference between f-SG and the TL-SG area was used to estimate the rest unfolding potential of the SG, the so-called residual SG expansion capacity (SG-REC, cm²).

Result: Mean f-SG diameter and area were 25.94 ± 2.94 mm and 5.36 ± 1.31 cm², respectively. The TL-SG area in the first postoperative CT was 3.99 ± 1.15 cm² resulting in a SG-REC area of 1.37 ± 0.87 cm². The SG-REC areas in acute and chronic AD were 1.15 ± 0.75 cm² and 1.89 ± 0.89 cm² (p < 0.001), corresponding to a 21.31 and 34.17% residual SG expansion capacity, respectively. The SG-REC area decreased to 0.73 ± 0.74 cm² after 1 year and to 0.52 ± 0.68 cm² in the last follow-up CT. In patients with a distal SG-induced new entry (dSINE) in follow-up, the SG-REC was increased in the first postoperative CT (1.84 ± 0.95 cm² vs. 1.32 ± 0.84 cm², p = 0.032).

Conclusion: Residual SG expansion capacity allows retrospectively the analysis of the counteracting between SG radial force within a compressed TL and indirectly the continuous stress of the intimal wall at the distal SG end. The residual SG expansion capacity was increased in chronic AD and in patients developed dSINE.

Publication History

Article published online:
19 February 2021