Abdominal aortic aneurism An abdominal aortic aneurysm (AAA) is a swelling of the abdominal aorta, the major blood vessel that carries blood from the heart to the rest of the body. It usually occurs in the section of the aorta that runs through the abdomen, but it can also occur in the thoracic aorta (the section that runs through the chest). An aneurysm is a weak spot in the wall of the blood vessel that bulges outward, like a balloon. As the aneurysm grows, it can put pressure on nearby organs and tissues and can also burst (rupture), which can be life-threatening. Symptoms of an AAA may include: A pulsating sensation in the abdomen Pain in the abdomen or back Fainting or dizziness Rapid heartbeat In some cases, an AAA may not cause any symptoms at all. It is often discovered during a routine checkup or imaging test done for another reason. Risk factors for developing an AAA include: Age (the risk increases with age)