What could cause an aortic aneurysm to burst?

Ruptured aneurysm: An abdominal aneurysm can rupture for many reasons. Most common is size. As the aneurysm enlarges the wall gets weaker. We know that aneurysms over 5 cm have a higher rupture rate and those should be operated on electively. Other factors making rupture more likely would be uncontrolled high blood pressure and infection in the wall of aneiurysm.