What is aortitis?
Aortitis is a condition where the aorta is inflamed. It is a form of vasculitis – inflammation of a blood vessel. More correctly, it is known as arteritis because the inflammation affects an artery. While every type of vasculitis has clinical implications, aortitis may be very serious due to the importance of the aorta in blood circulation. It compromises the supply of oxygen-rich blood to the entire body to some extent or the other and can therefore have devastating implications. Overall, aortitis is not a common condition but when it does occur, it can be life threatening even in mild cases.
Anatomy and function
The aorta is the largest artery in the human body. It arises from the left ventricle of the heart where it carries oxygen-rich blood recently received from the lungs. The aorta has several branches which carries this oxygenated blood to the entire body. In order to perform its functions, the aorta has a thick wall which is elastic. The thickness provides strength to withstand the high pressure of blood being pushed out of the heart. The elasticity provides recoil where it initially stretches and then ‘snaps’ back to its position to keep blood moving on throughout the course of the aorta.
Effects of an inflamed aorta
Inflammation is the body’s response to injury but the process disrupts the normal functioning of the affected part. When the aorta is inflamed it becomes dilated. With ongoing inflammation, the affected parts of the aorta may experience the formation of scar tissue. Ultimately the elastic recoil of the aorta is affected as well as the diameter of the aorta and its branches. Without blood being constantly propelled due to the loss of elasticity and not having a sufficiently wide passage to move through, there may not be enough oxygen-rich blood reaching every part of the body. The symptoms of aortitis can therefore vary depending on which area of the body is affected by less oxygen-rich blood.
Reasons for aorta inflammation
There are a number of reasons why the aorta may become inflamed. Trauma and infection of the aorta are two well understood causes of inflammation. Autoimmune diseases are conditions where the body’s immune system attacks its own tissue. It is sometimes targeted at the connective tissue within the artery wall and is also known as a connective tissue vascular disease.
Despite the number of known yet at times unexplained causes of aortitis, there are also instances where there is no known cause or mechanism to corroborate the reason for the inflammation of the aorta. These causes are broadly termed as idiopathic which means that as yet the cause is unknown. In terms of inflammation of an artery, Takayasu’s arteritis and giant cell (temporal) arteritis are two conditions of unknown causes that may involve the aorta.
The two most significant causes of aortitis are an infection or connective tissue disorders. However, these are not the only causes. Injury to the aorta through various means of trauma can also contribute to aortitis although it may be acute in this instance and resolve shortly thereafter. Injury of the aortic wall may also occur with diagnostic or surgical procedures although this is rare.
A number of different microorganisms can cause infectious aortitis, but bacteria are by far the main infectious factor. The bacteria are usually spread from neighboring sites of infection, or may be circulating in the bloodstream (bacteremia). Salmonella, staphylococci and streptococci are among the main groups of bacteria that cause aortitis. These microbes directly infect and cause inflammation of the wall of the aorta. Sometimes there may be cross reactivity as antibodies targeting various pathogens lodge in the wall of the aorta. In other cases, antibodies generated specifically against proteins in the aorta wall are the mediators of inflammation.
Connective tissue diseases
Similar to the immune mechanism that possibly causes aortitis following an infection, there are chronic conditions related to immune-mediated reactions that are not caused by an infection. Connective tissue diseases are a group of conditions where the body’s immune system attacks specific tissues. It is believed to be associated with genetic factors but may be triggered, although not caused, by an infection. Takayasu arteritis is one such type of connective tissue disease that leads to aortitis. However, its cause still remains largely unknown despite hypotheses about a genetic factor and immune mediated reaction.
The signs and symptoms of aortitis can differ based on the cause and the part that is affected, or more specifically its branches which are most affected. General symptoms that may be seen with different causes includes :
Blood pressure differences
High blood pressure (hypertension) may be seen as the aortic wall loses its elasticity and becomes narrowed. This may also occur when a branch of the aorta becomes narrowed, especially with the renal artery supplying the kidney. When the branches of the arm are affected, there may be a significant different in blood pressure between the left and right arm.
Although the heart rate and rhythm are usually not affected with aortitis, there may be a distinct difference in the pulse between the affected and unaffected limb. It may be more noticeable with certain movements like lifting the arm or turning the head.
Bruits are abnormal sounds as a result of disruption in blood flow. In aortitis, bruits may be audible over the abdominal aorta as well as some of its branches like the carotid and subclavian arteries or branches of these arteries, as is the case with a bruit over the brachial artery.
Various other symptoms may also be present but this is dependent on the underlying cause, affected vessel and severity of the condition. These symptoms may include :
- Malaise – a generalized feeling of being unwell.
- Claudication of the arms
- Joint pain
- Muscle aches
- Blurring of vision
Other symptoms may also arise as a result of complications of aortitis, such as a stroke and kidney dysfunction.
Aortitis can be divided into three distinct phases.
- Phase I – fever, fatigue, joint pains, weight loss and night sweat are non-specific symptoms and can be due to various other causes.
- Phase II – pain and tenderness over the affected vessel as the artery wall becomes inflamed.
- Phase III – reduced blood flow with symptoms of low oxygen availability of the affected area.
The clinical features of the disease may raise the concern about aortitis but further investigations are needed. Blood tests help to identify the most likely cause and confirm or exclude specific causes. However, various imaging techniques are necessary to verify the changes in the wall of the affected vessel and disruption to blood flow. These investigations include :
- CT angiography
- MR angiography
Arterial wall biopsy may also be considered where a minute amount of the tissue from the aortic wall is collected for further microscopic examination.
The video above is of a CT angiogram showing aortitis caused by Salmonella bacteria.
The treatment measures for aortitis may differ depending on the cause of the condition. It is important to note that untreated aortitis, whether mild, moderate or severe, is life threatening in the long term. Therefore treatment is intended to :
- halt the disease from progressing further
- treat and manage complications
- monitor for reactivation of the condition
The main drugs used in the treatment of aortitis are corticosteroids and immune suppressants. Corticosteroids help reduce inflammation and manage it long term. It also suppresses the immune system to some extent. Immune suppressants specifically suppress the immune system but should only be used if there is no existing infection. Other drugs that may anti-tumor necrosis factor agents and certain antibiotics.
Surgical procedures may of little use in the treatment of the condition itself. It is therefore mainly used in the treatment and prevention of complications, especially narrowed and sometimes occluded arteries.
- Angioplasty is used to widen the narrowed blood vessels.
- Stents may be inserted into the artery to keep it open.
- Bypass grafts create alternative pathways for blood to flow around the affected artery.