Definition Of Aneurysms and Dissections

Aneurysms and dissections are two types of potentially fatal disorders of the aorta. In aneurysm, a weak area in the wall of the aorta bulges out. In dissections, the layers of the arterial wall get separated. These disorders gradually develop over the years, but they are fatal when they occur. Aneurysms are not restricted to the aortic artery alone; they develop in smaller arteries too.

Before going to details We need to know what is an aorta ? The Aorta, arising from the left ventricle, is the largest artery in the body, with a diameter of approximately one inch at its widest point. The oxygenated blood from the left ventricle is pumped into the aorta, from which it is carried to the different parts of the body by the smaller arteries, branching off from it at different points. After the arteries to the head and the hands have branched off, the aorta doubles up on itself forming an arch over the heart, and then goes down along the spine giving out branches to the left and right, till it reaches the pelvis. At the pelvis, it bifurcates into the two iliac arteries that go down the legs.

The force exerted on the walls of the aorta, by the pressure of the blood passing through it, causes ballooning out of the weak points in the wall. These bulges are called aneurysms. This ballooning out, further thins out the walls of the aneurysms, eventually resulting in their rupture. If the rupture is minor, it may only cause a leak which can induce people into getting medical help due to the pain it causes. A small tear can be surgically repaired without further incident. However, a large rupture causes severe uncontrollable internal bleeding which almost always results in death.

The abdominal aorta is the part that is most prone to Aneurysms accounting for nearly 75% of all aortic aneurysms. Thoracic aorta which passes through the chest area is the next common site of aneurysms. Popliteal arteries at the back of the knee, femoral arteries in the thigh, carotid and cerebral arteries which supply to the heart and brain respectively, also may have aneurysms. Aneurysms in older people are found where arteries branch, possibly because of the turbulent flow of blood hitting the arterial walls at these places, weakening them. Tube-like or fusiform aneurysms are more common than rounded saccular aneurysms.

Atherosclerosis, which weakens the walls of the aorta, is usually the underlying cause of aortic aneurysms. Aortitis, which is an inflammatory disease of the artery, infectious diseases like syphilis and mechanical injuries to the arteries are also reasons for developing aneurysms. People with Marfan syndrome, which is an inherited connective tissue disorder, have aneurysms in the first part of the aorta called the ascending aorta. High blood pressure and smoking are known risks of aneurysms.

Due to the sluggish blood flow within the aneurysms, the chances of blood clot formation are very high. Sometimes, the walls of the aneurysms may be lined by a layer of clotted blood. The risk of blood clots breaking away and travelling along the arteries as emboli and finally causing blockage in smaller arteries, is also quite high. Popliteal arteries with aneurysms are more susceptible to emboli formation. Calcification of the walls of aneurysm also occurs in many cases.

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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