Tissue factor levels and the fibrinolytic system in thin and thick intraluminal thrombus and underlying walls of abdominal aortic aneurysms

Background The hemostatic system cooperates with proteolytic degradation in processes allowing abdominal aortic aneurysm (AAA) formation. In previous studies, it has been suggested that aneurysm rupture depends on intraluminal thrombus (ILT) thickness, which varies across each individual aneurysm. We hypothesized that hemostatic components differentially accumulate in AAA tissue in relation to ILT thickness. Thick (A1) and thin (B1) segments of ILTs and aneurysm wall sections A (adjacent to A1) and B (adjacent to B1) from one aneurysm sac were taken from 35 patients undergoing elective repair. Methods Factor levels were measured using enzyme-linked immunosorbent assay of protein extract. Results Tissue factor (TF) activities were significantly higher in thinner segments of AAA (B1 vs A1, P = .003; B vs A, P P P = .001). Significantly higher tissue plasminogen activator was found in thick thrombus-covered wall segments (A) than in B, A1, and B1 ( P = .015, P P 2 -antiplasmin in thin ILT adjacent walls (B) were higher compared with wall (A) adjacent to thick ILT ( P = .021) and thick ILT (A1; P r = 0.55; P = .004). Conclusions These results suggest that higher TF activities are present in thinner AAA regions. These parameters and local fibrinolysis may be part of the processes leading to destruction of the aneurysm wall.