An aortic aneurysm is a swelling or bulge in the aorta, the main blood vessel that runs from the heart down through the chest and stomach. Untreated aneurysms can grow over time and may eventually rupture or dissect, both of which are life-threatening emergencies requiring immediate medical care. The most common symptom of a ruptured aneurysm is a tearing or ripping sensation in the chest or back followed by severe pain, but some ruptures cause no symptoms until death occurs from massive internal bleeding.