Abdominal aortic aneurysm (AAA) rupture is the 13th commonest cause of death in the Western World. Although considerable research has been applied to the aetiology and mechanism of aneurysm expansion, little is known about the mechanism of rupture. Aneurysm rupture was historically considered to be a simple physical process that occurred when the aortic wall could no longer contain the haemodynamic stress of the circulation. However, AAAs do not conform to the law of Laplace and there is growing evidence that aneurysm rupture involves a complex series of biological changes in the aortic wall. This paper reviews the available data on patient variables associated with aneurysm rupture and presents the evidence implicating biological factors in AAA rupture.

Circulating IL-6 is elevated within the aorta in patients with aneurysms and corresponds to aneurysm position. Furthermore, aneurysm surface area and mean plasma IL-6 are correlated. In the absence of any evidence of systemic inflammation in the form of elevated hs-CRP, these data support the hypothesis that aneurysms secrete IL-6 into the circulation. This may contribute to the high cardiovascular mortality observed in patients with aneurysms.

In conclusion, these findings support the role of MMPs in AAA pathogenesis. Elevation of MMP9 was associated with ruptured aneurysm related 30-day mortality and may represent a survival indicator in this group.