What is Abdominal Aortic Aneurysm?

March 11 21:25 2019 Print This Article

It is defined as a condition in which there is a swelling of the abdominal aorta. It is also referred as an AAA. The abdominal aorta exceeds its diameter by more than 50 percent. The degeneration of aortic wall leads to this condition but the exact reason is still uncovered. The triple A conditions in 90 percent of the cases occur below the kidneys and is known as the infra renal. However, in 10 percent of the cases it occurs at the level of kidney or above the level of kidney which are known as the pararenal and suprarenal respectively. They may extend to the pelvis and may involve both of the iliac arteries. This triple A condition occurs among individuals in the 6 and 7th decade of their life. It is common in the males as compared to females.

The smokers are more prone to this condition. Initially, the condition is asymptomatic and it may lead to the pain in abdomen, back and legs which may occur due to the surrounding tissue and lead to the disturbed blood flow. It may lead to the rupture which may be life threatening condition. A large quantity of blood is spilled into the abdominal cavity. The large and symptomatic condition of triple A is treated with the help of surgery. For surgery to occur its size must be more than 5.5 cm in diameter. The screening is not much successful in some cases.

What is the prognosis of abdominal aortic aneurysm?
In order to determine the risk rupture the diameter is an important factor to decide it. It has been observed that the smaller aneurysm with the diameter less than 5.5 cm are more likely to rupture as compared to the larger aneurysm with the diameter more than 5.5 cm. Around one fourth of the ruptured triple a have diameter less than 5 cm. Around two third of the ruptured triple a were stable. They were having the diameter more than 5 cm. Another author gave the finding that out of 473 subjects only 7 percent of the cases succumb to rupture before the need of surgery arises and they have a diameter less than 5 cm. Around one fourth of the cases were stable and did not require any surgery and have a diameter more than 5 cm. There are other ways by which the rupture assessment can be made.

The engineering technique is very helpful to do the numerical analysis of triple a condition. It involves the finite element method to determine the wall stress distributions. This stress distribution is related to the geometry of AAA and not on the diameter. The wall stress is not the single factor which determines the rupture assessment. It ruptures when the wall stress is more than the wall strength. The rupture assessment can be more accurate with the patient specific wall stress and the patient specific wall strength are combined. There is a new method to determine the patient specific wall strength which is non invasive. It is also supported by the tensile testing.

The other methods which determine the rupture risks are triple a wall stress, triple a expansion rate, asymmetry, presence of intra luminal thrombus, rupture potential index and a finite element analysis rupture index. The bio chemical factors along with the computer analysis also play a crucial role. The growth of ILT and the parameters of AAA and the mathematical models also have an important role in it.

What is the epidemiology and history of abdominal aortic aneurysm?

It is not found among the people of Africa, Asia and Hispania. In the U.S alone it kills around 15000 people per year. It is secondary to the AAA rupture. It varies its frequency between the males and females. It is most common in the males who smoke and are aged between 60 to 70 years old. The risk of this condition increases with increase in the smoking and vice a versa. The other risk factor is the hypertension.

The rupture of aaa occurs around 2 percent of the man and has a very high mortality rate. Their historical records date back from the ancient Rome and the Greek surgeon were involved in it. It occurred in the second century A.D. The triple A condition was treated with the help of ligatures which are proximal and distal. They gave the central incision and remove the thrombotic material from aneurysm. The surgical treatments were not successful in treating this condition. The New Greek surgeon in the year 1923 performed the first successful aortic ligation. There are other methods which are successful in treating the triple A condition.

It includes the wrapping of aorta by cellophane paper. It causes fibrosis and slows down the growth of aneurysm. A patient survived for 5 years when he used this technique on him. The endo vascular aneurysm was performed in the late 1980s and was followed later on.

What are the future directions of abdominal aortic aneurysm?

There are many ways by which the rupture risk assessment can be done. The approach which is based on the bio mechanics is much more successful than the current diameter approach. The numerical modeling is more successful to calculate the wall stress. It tells about the rupture potential of an aneurysm. There are many experimental results which support these numerical results. It tells about the bio mechanical behavior of triple A along with their material strength which varies. They can be weak or strong and include the areas of calcification.

The novel technique helps to make the experimental models which involve the injection molding technique which makes patient specific triple A replicas. A more realistic material analogue is being developed. A new range of silicone rubbers has been created so that the different properties of triple a can be easily accommodated. These models are also used in the experiment testing by the use of photo elastic method from the stress analysis. This helps to determine the location of rupture with the numerical prediction. As the advances in the research are increasing the increase in callobration between the engineers and doctors may lead to the stronger future research.

In the U.S it is the 13th leading cause of death and the 10 th cause of death among the men with age above 55. An animal study was published in the journal of Nature Medicine which showed that the removal of a single protein may cause injury to the blood vessels. It can cause a lethal complication of atherosclerosis. When the gene known as cyclophilin A was removed it gave a complete protection from the triple A. Moreover, new devices are developed so that the more complex form of these conditions can be treated.

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