Abstract
Background The intraluminal thrombi (ILT) of abdominal aortic aneurysms (AAA) contain neutrophils,
which can secrete elastase. We evaluated whether plasma neutrophil elastase-derived
cross-linked fibrin degradation products (E-XDP) could reveal the presence, size and
mechanical stress of AAAs and its ILTs.
Methods E-XDP and D-dimer were measured in plasma from 37 male patients with AAA and 42 male
controls. The ILT volumes of the AAAs and any coexisting aneurysms could be measured
in 29 patients and finite element analysis was performed to estimate mechanical stress
of the ILT. E-XDP, neutrophil elastase and neutrophil marker CD66acd were evaluated
in aortic tissue with immunohistochemistry (IHC). The association between ILT volume
and E-XDP was validated in a separate cohort (n = 51).
Results E-XDP levels were elevated in patients with AAA compared with controls (p = 5.8e-13), indicated AAA with 98% sensitivity, 86% specificity and increased with
presence of coexisting aneurysms. The association between AAA and increased E-XDP
was independent of smoking, comorbidities and medication. E-XDP correlated with volume
of all ILTs (r = 0.76, p = 4.5e-06), mean ILT stress (r = 0.46, p = 0.013) and the volume of the AAA-associated ILT (r = 0.64, p = 0.00017). E-XDP correlated stronger with ILT volume compared with D-dimer (r = 0.76 vs. r = 0.64, p = 0.018). The correlation between E-XDP and ILT volume was validated in the separate
cohort (r = 0.53, p = 7.6e-05). IHC revealed E-XDP expression in the ILT, spatially related to neutrophil
elastase and neutrophils.
Conclusion E-XDP is a marker of the presence of AAA and coexisting aneurysms as well as the
volume and mechanical stress of the ILT.
Keywords
thrombus - leukocyte elastase - aortic aneurysm - abdominal - finite element analysis
- computed tomography
