An aortic aneurysm is a permanent enlargement of a part of the aorta. Aneurysms form when the aortic wall weakens due to deterioration of its cells. The aorta then loses its flexibility, and can’t expand and compress normally, finally weakening up to a point where it simply bulges in size. If the diameter of the aorta expands over 50 percent of its normal size, we’re talking about aortic aneurysms.
Large aneurysms can compress nerves and organs, leading to pain, discomfort, or an inability to function normally. Blood clots can also form on the aortic wall, and they can later detach and cause a stroke or a heart attack. The most serious problem can occur if the damaged wall bursts. Because the aorta is the main artery in your body, its rupture creates a massive internal bleeding, which can happen so fast that roughly half of the patients die on their way to the hospital.
How do aortic aneurysms develop?
The aortic wall consists of three layers:
- The inner layer (intima), which allows uninterrupted blood flow.
- The middle layer (media), mostly made of elastic fibers and very little muscle.
- The outer layer (externa), made of collagen and elastic tissue.
As you can see, the aortic wall is mostly made up of connective tissue. Collagen preserves the wall's stiffness and tension, while elastin maintains a flexible structure despite constant pressure. Aneurysms form as a result of destruction of these proteins. If elastin is destroyed, the body reacts by creating more collagen.
The smooth muscle cells found in the innermost layer of the aortic wall, besides forming the lumen, also “fixes” connective tissue, so the destruction of these cells may also contribute to aneurysm development.
Other factors that make aneurysm formation more likely include various infections and autoimmune processes, as well as injuries to the aorta (blunt trauma).
Of course, only one of these mechanisms usually isn’t enough to cause severe damage. Aneurysms form as a result of complex processes, which are a product of biological (inflammation, protein breakdown), and mechanical factors (such as high blood pressure).
What are the risk factors for aortic aneurysms?
Generally, aneurysms share the same risk factors as all cardiovascular diseases.
The main cause of aneurysms is atherosclerosis, a condition where plaque (made of cholesterol, fat, and calcium) is formed on the internal walls of your arteries. The arterial lumen is then narrowed, which results in impaired blood flow. As a result, organs do not receive enough oxygenated blood.
Because atherosclerosis is the main cause of aneurysms, the risk factors for these two diseases are so similar that it was once thought that aneurysms are just manifestations of atherosclerosis.
Risk factors can be classified into two main groups:
Factors you can’t control, such as:
- Age. The frequency of aneurysms rises with old age. People over 60 have the highest rate of aneurysms, mostly because the elastin and collagen ratio is reduced at that age.
- Gender. Men are four to five times more likely to have aneurysms, probably due to differences in hormones.
- Race. Caucasians are far more likely to be diagnosed with an aneurysm than black people.
- Genetic factors. Between one quarter and one third of people with an aneurysm have a first-degree relative with a similar disease.
- Genetic disorders, and specifically connective tissue diseases such as Marfan or Ehlers-Danlos syndrome, which cause tissue abnormalities, making the protein-rich structures in the aortic wall more susceptible to breakdown.
- Birth defects. People are normally born with three leaves on the aortic valve, whose purpose is preventing blood flow from the aorta back to the heart. Some people have only two leaves, and that condition can be associated a higher risk of an aneurysm.
- Having an aneurysm in a different place. The risk of also having an aortic aneurysm are statistically higher if you already have an aneurysm in a different large artery.
Factors you can control include:
- Smoking represents the strongest risk factor both in aneurysm formation and aneurysm rupture. Besides directly damaging the blood vessels, smoking speeds up plaque development and increases blood pressure during this process. Almost half of patients with diagnosed aneurysm are smokers. Besides that, if you stop smoking, the risk for developing an aneurysm stays the same for at least ten years.
- High blood pressure. Increased blood pressure also raises the pressure on the aortic wall, making it weaker and more prone to expansion. It’s interesting that women are at higher risk in this category.
- High cholesterol levels. High levels of fat and cholesterol lead to the cholesterol plaque, thereby slowing and eventually blocking blood flow through the arteries.
- Tissue hypoxia. If aortic tissue doesn’t receive oxygenated blood as it would normally, it can lead to aortic wall destruction, which then sets the process of aneurysm formation in motion.
- Obesity. People with weight issues, specifically in their belly area, are more prone to aneurysms.
- Stress contributes to high blood pressure.
- An inactive lifestyle contributes to some of the previous risk factors, meaning that people who lead a sedentary life are at risk of high cholesterol, which can lead to obesity as well as high blood pressure.
Almost one quarter of all deaths are caused by cardiovascular diseases. Abdominal aneurysms are in the top 15 causes of death in the general population. Early diagnosis is essential for preventing complications, such as aortic rupture or dissection.