A morphologic study of chronic type B aortic dissections and aneurysms after thoracic endovascular stent grafting.

BACKGROUND: The long-term results of treating chronic aortic dissections and aneurysms in association with dissections with thoracic endovascular aortic repair (TEVAR) are unknown, and the timing for intervention is uncertain. We evaluated the morphology of stent graft and aorta remodeling and the volumetric changes in these patients after successful TEVAR.

METHODS: Serial computed tomography scans of 32 patients who underwent TEVAR for uncomplicated chronic dissections (group A, n = 17) and chronic dissections with aneurysms (group B, n = 15) were analyzed at 1, 6, 12, and 36 months. Stent graft diameter changes and positional migration were assessed three-dimensionally using Mimics 14.0 (Materialize, Leuven, Belgium). Volumetric data for true lumen, false lumen, thrombus load, and aortic size were measured by Aquarius iNtuition 4.4 software (TeraRecon, San Mateo, Calif). Results were compared between the two groups and with stent graft diameter, length, and oversizing.

RESULTS: Aortic stent grafts remodeled progressively, with inlet area increasing 4.4%, 10.1%, and 14.2% and outlet area increasing 42.6%, 67.2%, and 72.3%, respectively, at 6, 12, and 36 months. True lumen volume increased progressively in group A (114 to 174 mL) and group B (124 to 190 mL) from baseline to 36 months. False lumen volume decreased in group A (150 to 88 mL) and group B (351 to 250 mL), whereas thrombus load in the false lumen increased from 73% to 80% in group A and 84% to 87% in group B in 3 years. Eight patients (4 in each group) showed an increase in total aortic volume of >10%, 12 showed a static volume, and 12 showed shrinkage. Aortic volume change had no relationship to pathology, stent graft sizing, and thrombus load but was positively associated with the placement of a longer graft. A small but progressive distal migration of stent grafts was noted in all patients (3.1, 4.5, and 5.1 mm at 6, 12, and 36 months) but was more prominent in shorter stent grafts (≤ 162 mm). No deaths, rupture, or secondary interventions occurred during follow-up.

CONCLUSIONS: Aortic remodeling after TEVAR in chronic dissection is a continuous process. There were no significant differences between chronic dissections and aneurysms in all volumetric parameters. Treating chronic dissections early, before aneurysm formation, did not appear to have a morphologic advantage.