An aneurysm is an enlargement or bulging in an artery caused when the arterial walls weaken or suffer damage. The weakening of the arterial walls reduces the artery’s ability to handle normal blood pressure, and can eventually lead to an arterial rupture and internal bleeding. When this condition occurs in the aorta, it is called an aortic aneurysm. The aorta is the artery which provides oxygenated blood from the left ventricle of the heart to the rest of the body. The development of an aneurysm can block oxygenated blood supply to the body, leading to organ failure and even death.
Aneurysms are caused by damage to arterial walls; however, arterial walls are not a homogenous tissue. Arterial walls are composed of three layers, the adventitia (outermost layer), the media (middle layer), and the intima (innermost layer). The exact condition is dependent upon layers becoming damaged. A true aneurysm requires enlargement of all three layers of the arterial wall. A false aneurysm occurs only in the media and adventitia, and has a higher risk of bursting. This condition is typically the result of an infection. A third condition, an aortic dissection occurs when there is a separation in the vessel wall, causing blood to leak between the gaps. This bleeding causes damage to the arterial wall, and increases the risk of rupture.
Since the aorta circulates blood throughout the entire body, there is a possibility for aneurysms to develop throughout the arterial system. The most common sections of the aorta that develop aneurysms are in the brain arteries and abdominal aorta. While these can be serious, aortic aneurysms are often slow growing. However, aneurysms typically do not present symptoms until they are very large, or have ruptured. For this reason, aneurysms may go undetected for years, until they pose a serious health risk.
Large aneurysms may cause patients to experience chest or back pain. Some patients may not develop pain, but may notice regular or irregular sensations or “unusual feelings” in their upper chest or lower back. Patients may also experience a pulsating bulge in the abdomen, fullness following minimal (less than usual) food intake, vomiting, or nausea.
Once the arterial wall has ruptured, patients will begin to suffer from internal bleeding. This poses a serious risk, as severe blood loss can occur as well as damage from internal bleeding. Rupturing of the artery can cause a drop in blood pressure, leading to light-headedness, weakness, shortness of breath, confusion, initial tachycardia, sweating, numbness or tingling, or loss of consciousness. If bleeding becomes uncontrolled, blood pressure can drop dangerously low, which can lead to shock. As blood supply to the body decreases, vital organs may begin to fail, and loss of consciousness will occur. As the heart attempts to provide sufficient blood supply to the body, the heart rate will increase. Eventually, the heart will become overworked and stop beating (cardiac arrest).
References:
http://www.emedicinehealth.com/aortic_aneurysm