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Abdominal, thoracic and ascending aortic aneurysm

Abdominal aortic aneurysm (called AAA or triple A) is a condition in which abdominal aortic wall dilatation of at least 50% of the normal caliber occurs .

Anatomy of the aorta

The aorta :

  • It originates from the upper part of the left ventricle,
  • It goes up to the cervical spine(ascending aorta),
  • It then descends downwards (aortic arch) across the chest area (descending or thoracic aorta) and the abdomen (abdominal aorta).

The aorta carries oxygenated blood pumped from the heart to the rest of the body.

The abdominal aorta begins at the diaphragm and descends to the 4th lumbar vertebra where it divides to form the common iliac arteries. 
The function of the abdominal aorta is that of bringing oxygenated blood to the abdominal and pelvic structures in the body.

 

 

 

The diameter of the aorta is:

Men’s Women
Ascending aorta 3.71cm 3,45cm
Down aorta 2,82cm 2,54cm

Fonte: Kalsch H, Lehmann N, Mohlenkamp S, et al. Body-surface adjusted aortic reference diameters for improved identification of patients with thoracic aortic aneurysms: results from the population-based Heinz Nixdorf Recall study. International journal of cardiology. 2013;163:72–8.

The rupture of the aneurysm  can cause a dangerous and deadly bleeding.

The most frequent location of arterial aneurysms is in the abdominal aorta, in the segment of the artery below the kidneys. 
An abdominal aneurysm at this level is called an infrarenal aneurysm. 
An aneurysm can be classified based on:

  • Location,
  • Shape,
  • Cause.

This swelling can form anywhere, but occurs especially along the arteries:

  • In the abdomen,
  • In the brain,
  • On the chest.

 

Types of aneurysm based on location

An aneurysm can develop anywhere along the aorta:

  1. An aneurysm that forms in the aorta section that passes through the abdomen (the abdominal aorta) is called the abdominal aortic aneurysm .
  2. An aneurysm that forms in the chest area is called a thoracic aortic aneurysm and may involve the aortic root, ascending aorta, aortic arch, or descending aorta.
  3. An aneurysm that involves the aorta in the stretch between the abdomen and the chest is called a thoracoabdominal aortic aneurysm .

Aneurysms may develop in other blood vessels:

  • The popliteal vessels of the leg: an aneurysm of the femoral artery behind the knee
  • Visceral vessels: an aneurysm in the artery of an internal organ.

Among the visceral arteries that may have an aneurysm are:

  • The renal artery to the kidneys,
  • Splenic artery to the spleen,
  • The hepatic artery to the liver,
  • The pulmonary artery to the lungs (rare),
  • The superior mesenteric artery to the stomach and intestines.

 


Classification of aortic aneurysms

The Stanford classification divides the dissections into type A and type B:

  • Type A involves the ascending aorta and the arch. The ascending aorta is between the aortic annulus and the brachiocephalic trunk or brachiocephalic artery.
  • Type B does not involve the ascending aorta. The descending aorta is located after the left subclavian artery.

The DeBakey rating:

  • Type I: aorta, aortic arch and descending aorta (30%).
  • Type II: only the ascending aorta (20%).
  • Type III: distal descending aorta to left subclavian (50%).

One variant of this problem is the dissecting aortic aneurysm.

Dissection of the aorta

Anatomy
A blood vessel consists of three layers:

  • Intimate (inner layer made of endothelial cells),
  • Average (containing muscle elastic fibers),
  • Adventitia (external connective tissue).

Aneurysms can be either true or false. 
The wall of a true aneurysm involves all layers. 
The wall of a false aneurysm (pseudoaneurysm) involves only the outer (adventitial) layer.

A dissection of the aorta begins with a thinning of the inner layer of the artery wall. 
When a detachment occurs in the innermost layer, the blood is channeled to the wall and causes the inner layer to separate from the wall of the others. 
This causes a weakening of the aortic wall with a high potential for rupture.

The middle layer of the aorta imparts tensile strength and elasticity to this blood vessel. 
This layer is composed of several structural proteins, in particular:

  • Collagen,
  • Elastin

The composition of the aortic wall depends on the area:

  • In the ascending part there is much elastin,
  • In the descending thoracic and abdominal part there is a progressively reduced elastin content and more collagen. This is why an aneurysm is most likely in the lower part of the descending aorta.

In addition, in this area there are more enzymes that degrade structural proteins . 
The consequences are a wall:

  • Weaker,
  • More rigid.

High blood pressure promotes aneurysm dilatation.

Aortic dissection can be a dangerous emergency situation .

1. Dissection is acute when a diagnosis is made within 14 days of onset. 
2. If the duration is higher then chronic dissection is defined.

 

Causes of abdominal aortic aneurysm

An abdominal aortic aneurysm can be caused by several factors that determine the destruction of the aortic wall proteins that are necessary for its stabilization. 
The exact cause is unknown.

It is believed that atherosclerosis (fat and cholesterol deposits ) plays an important role in aneurysmal disease.

The risk factors for atherosclerosis are as follows:

  • Age (over 60 years),
  • Male gender (the pathology in the male gender is four or five times higher than in the female gender),
  • Family history (first degree relatives, such as father or brother),
  • Inheritance, the aneurysm can be hereditary (genetic),
  • Hyperlipidemia (high levels of fat in the blood),
  • Hypertension ( high blood pressure ),
  • Smoke ,
  • Diabetes,
  • Obesity .

Other diseases that can cause an aortic aneurysm are as follows:

  • Genetic diseases : connective tissue diseases such as Marfan syndrome, Ehlers-Danlos  syndrome and Turner syndrome . 
    Marfan syndrome can cause dilatation of the basal part of the aorta or aortic bulb, that is, the one that includes the valve and the aortic ring.
  • Congenital syndromes (present at birth) such as the bicuspid aortic valve and coarctation of the aorta,
  • Giant cell arteritis  (a disease that inflames the temporal arteries and other blood vessels of the head and neck, reducing blood flow to the affected areas and causing persistent headache and loss of vision ),
  • Trauma,
  • Aortitis: infection of the aorta caused by pathogens such as syphilis , salmonella or staphylococci . These infectious diseases are rare.

Signs and symptoms of aortic aneurysm

The symptoms of this condition may be different depending on the position.

Usually, the aortic aneurysm grows slowly and causes no symptoms. 
In most cases aneurysm rupture never occurs. 
Generally, this dilatation is small and remains small, although it may expand over time. In this case, it may cause symptoms. 
The growth rate of an aortic aneurysm is difficult to predict.

 

Symptoms of thoracic aortic aneurysm

Symptoms may occur:

  • If the aneurysm is large and pressing against the structures in the center of the chest (for example, the recurrent laryngeal nerve), it can affect swallowing, phonation (voice) and breathing.
  • In case of breakage.

The symptoms of thoracic aneurysm are more important when the aneurysm is located in the arch. 
The symptoms of thoracic aortic aneurysm are as follows:

In case of rupture of the aneurysm, there is a strong  drop in blood pressure . 
This condition requires immediate medical intervention because it can cause sudden death.

 

 

 

 

Symptoms of abdominal aortic aneurysm
The aneurysm may cause:

The intensity of the pain can vary from mild to severe and is not affected by movement. 
Some positions, such as sitting or lying down, may be more comfortable than the standing position. 
Young people are especially susceptible to this type of aneurism.

 

Symptoms of aortic aneurysm rupture

When a rupture occurs, the blood flow is reduced in the lower part of the body and the consequences are:

Mortality from aortic rupture is very high: between 70 and 90% do not reach the hospital alive.

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