If it has already dissected it's obviously too late. The parent comment asked if it would prevent dissection in those aneurysms that haven't yet dissected which is probably a more complicated question. It would probably depend on the elasticity of the vessel since we don't see dissection exclusively on absurdly dilated aortas. At the very least we can guess that it would help to extend the life of the native artery. Of course only long term monitoring of these patients will give us a somewhat conclusive answer.
It's not always the aneurysm that causes the dissection. Sometimes the dissection causes the aneurysm. The theory is that a plaque tears a he in the surface of the aorta.
