Is increased thrombin activation in patients with abdominal aortic aneurysms dependent on area or volume of aneurysm thrombus mass?

OBJECTIVES: Does thrombin activation seen in patients with abdominal aortic aneurysms (AAA) relate to the thrombus surface area or volume within the aneurysm?

PATIENTS AND METHODS: A total of 130 patients with AAA were analyzed regarding levels of the complex between activated protein C-protein C inhibitor (APC-PCI) and AAA morphology. Analysis of APC-PCI complex was made using a sandwich immunofluorometric method.

RESULTS: Increased APC-PCI concentrations were seen in patients with AAA (0.44 microg/L; P < .001 compared with controls). The correlations of APC-PCI values were r = .13, P = .13 for aneurysm size, r = .08, P = .35 for thrombus surface area, and r = .13, P = .14 for thrombus volume. APC-PCI values elevated to 0.45 microg/L in 10 patients with AAA having no or very little thrombus mass.

CONCLUSION: Disappointingly, no correlation was found between thrombus surface area or volume and levels of the APC-PCI complex. Mechanisms other than the AAA-sac thrombus must be evaluated as cause of thrombin activation in patients with AAA.