Coagulation and fibrinolysis in the abluminal layer of the thrombus within abdominal aortic aneurysm

Abstract

Background. The development of intraluminal thrombus in the abdominal aortic aneurysm (ILT) is a natural reaction to lesion of the arterial wall. Local haemostatic processes and secondary thrombolysis in the intraluminal thrombus, through the stimulation of proteolysis in extracellular matrix, may constitute one of the factors that lead to aneurysm rupture. In our study, we evaluated the coagulation and fibrinolytic parameters in the abluminal layer of the thrombus within the aneurysmal sack in order to find the differences between the thin (≤ 10 mm) and the thick parts.
Material and methods. The sections sampled for the study were harvested from the thick (> 25 mm) and thin (≤ 10 mm) slices of the ILT obtained from the same 32 abdominal aortic aneurysms, namely from the layer directly adjacent to the aneurysmal wall. The tissue factor activity, antiheparin and antithrombin activity, plasminogen content, plasminogen activator levels and concentration of D-dimers in the samples were measured.
Results. The activities of the tissue factor and antiheparin activity in the abluminal layer of the ILT were statistically significantly higher in the thin thrombi than in the thick ones (p < 0.001). Thin thrombi revealed significantly higher plasminogen (p < 0.001) and D-dimer (p < 0.01) concentrations when compared to thick thrombi, while the activity of plasminogen activators was higher in the thick thrombi (p < 0.05).
Conclusions. The abluminal layer of the thin thrombus (up to 10 mm) of the abdominal aortic aneurysm shows higher activities of coagulative processes when compared to thicker thrombi (> 25 mm); moreover, this site reveals strong secondary activation of the fibrinolytic system. Further investigation of the association between coagulation/fibrinolytic activity and proteolysis occurring within the AAA wall requires evaluation of such processes with regard to differences in the thickness of the thrombus.