Body Height and Stentgraft Diameter Drive Thrombus Formation After Frozen Elephant Trunk Repair: A Risk-Focused Analysis.

BACKGROUND

Intraluminal thrombus formation is an increasingly recognized complication after frozen elephant trunk (FET) repair. This study aims to identify the key factors driving thrombus risk, and to characterize the prognostic impact of thrombus on long-term survival.

METHODS

Retrospective single-center analysis of 458 patients undergoing FET repair between 2013 and 2024. Parameters were evaluated for association with new intraluminal thrombus formation using Fine-Gray competing risk regression. Thrombus risk was visualized using a height-stentgraft diameter risk heatmap. Estimated intraprosthetic blood velocity was analyzed by receiver-operating-characteristic analysis and restricted cubic splines.

RESULTS

Sixty patients (13.1%) developed new intraluminal thrombus during a median follow-up of 3.2 years (IQR 1.1-5.5). In multivariable analysis, the standardized stentgraft-to-patient-height-ratio was independently associated with new thrombus formation (HR 1.55 [95% confidence interval 1.11-2.16]; p=0.009), alongside fresh frozen plasma transfusion (HR 1.46 [95% CI 1.00-2.13]; p=0.049). The risk-heatmap demonstrated highest adjusted thrombus risk in short-statured patients receiving large-diameter stentgrafts. Estimated intraprosthetic blood velocity was significantly lower in patients who developed thrombus; an optimal velocity threshold of 14.4 cm/s (area under the curve 0.644; sensitivity 82.8%, specificity 43.2%) was associated with a 3-fold higher thrombus rate below vs. above this threshold (16.1% vs. 5.0%). Maximum thrombus diameter was an independent predictor of death within the thrombus subgroup (HR 1.130 [1.041-1.227] per mm; p=0.004).

CONCLUSIONS

Post-FET thrombus risk is highest when a disproportionately large stentgraft is implanted in a short-statured patient; reduced intraprosthetic blood velocity may represent a contributing hemodynamic mechanism, a hypothesis-generating finding that requires prospective validation.