Computational fluid dynamics analysis for enlargement of the descending aorta after frozen elephant trunk implantation

Acute type A aortic dissection (ATAAD) treated with total arch replacement (TAR) plus frozen elephant trunk (FET) can achieve favorable early remodeling; however, late enlargement of the distal descending aorta still occurs in some patients. Study 1 included ATAAD patients who underwent TAR with FET between January 2015 and December 2023 and achieved complete false-lumen obliteration at the distal FET level. We identified cases with more than 5 mm enlargement at the distal FET level during follow-up and performed statistical analyses. Among these, patients with contrast-enhanced CT were analyzed using CFD. Study 2 used idealized aorta–stent graft models with different aorto-stent graft angles (AS angle) to isolate the hemodynamic effect of angulation. In Study 1, larger AS angle was associated with subsequent aortic enlargement, and a cutoff around 38.3° suggested higher risk. CFD tended to show disturbed/recirculating flow along the lesser curvature in high-angle cases, with lower WSS and higher OSI at the distal FET level. In Study 2, increasing AS angle accentuated lesser-curvature flow disturbance and increased greater-curvature WSS; Pearson correlations suggested a positive association between AS angle and greater-curvature WSS/TAWSS. A larger AS angle may be associated with enlargement of the distal aorta after FET. Larger and more precise studies are warranted to validate these findings.