Linking factor XIII activity to all-cause mortality after myocardial infarction: the overlooked role of serum albumin.

Background: Acute myocardial infarction (MI) remains a major cause of morbidity and mortality despite therapeutic advances. Factor XIII (FXIII), a fibrin-stabilizing enzyme with roles in coagulation, inflammation, and tissue repair, has emerged as a potential biomarker in MI. While low FXIII activity has been linked to adverse outcomes, the underlying determinants and its independent prognostic value remain unclear. Methods: In this retrospective study, FXIII activity was measured in 926 MI patients treated at University Hospital Würzburg between 2018 and 2023. Blood samples were collected within 24 h of cardiac catheterization. FXIII activity was assessed photometrically, and patients were followed for all-cause mortality. Multivariable regression and Cox models were used to identify predictors of FXIII activity and mortality. Results: Median FXIII activity was 110 %. Lower FXIII activity was associated with older age, female sex, lower albumin, higher CRP, and reduced kidney function. While crude mortality at 30 days and 1 year was significantly higher in patients with FXIII ≤ 110 %, FXIII activity was not an independent predictor of mortality after adjustment. Key predictors included albumin (HR = 0.221, p < 0.001), age (HR = 1.048, p < 0.001), eGFR (HR = 0.988, p = 0.001), and ASAT (HR = 1.001, p = 0.002). Conclusions: Although lower FXIII activity is associated with higher mortality post-MI, this effect is largely mediated by albumin levels. Albumin appears to be a central determinant of both FXIII activity and prognosis, highlighting its potential role as a key marker in risk stratification. Further studies are warranted to explore therapeutic implications of hypoalbuminemia in MI.