I think strictly speaking it was an aortic dissection that killed John Ritter, not an aneurysm. Aneurysms grow slowly, and like a balloon, the wall thickness go

I think strictly speaking it was an aortic dissection that killed John Ritter, not an aneurysm. Aneurysms grow slowly, and like a balloon, the wall thickness goes down as the vessel circumference increases. So then it can suddenly leak. The aneurysm is chronic (though often asymptomatic), the leak is usually sudden and catastrophic. An aortic dissection is a sudden tear in a usually non-aneurysmal aorta, if the leak goes all the way through it's usually immediately lethal, but often the pressure of blood "dissects" (separates) the inner and outer walls of the aorta, leading to all sorts of weird symptoms, which is why it is often misdiagnosed (A vascular surgeon was once reported to have said about aortic dissection that the "the standard of care is to miss the diagnosis", because it so often mimics other conditions, both benign and dangerous. )