The aorta is the largest artery in the body. It rises from the heart's left ventricle (the major chamber that pumps blood out of the heart) and is filled with oxygen-rich blood that travels throughout the body.
An infection can develop in the aorta two different ways:
- Mycotic aneurysm
- Aortic graft infection
Mycotic aneurysms occur when an infected mass, known as a septic embolism, is found in the heart. An embolism can be made of a number of different materials including blood clots, cholesterol and fat. A septic embolism that results in a mycotic aneurysm is often the result of inflammation in the inner heart tissues (infective endocarditis) that is generally caused by bacteria. When the bacteria that is causing the infection gathers into a mass, it becomes a septic embolism that may then travel to the aorta. In some cases, the aorta coming in direct contact with the bacteria may lead to inflammation and the formation of an aneurysm.
Some patients may have a history of an aortic graft being performed. This procedure generally uses synthetic materials to bridge two sections of the aorta together in order to replace a damaged or defective portion of the blood vessel. This grafted section of the aorta may become infected after the procedure if it was exposed to bacteria during the surgery or there was persistent bacteria in the bloodstream affecting the recovering area.
Symptoms of aortic infection may vary depending on the type of infection and its location. When the infection is due to a mycotic aneurysm, symptoms are usually noticed prior to diagnosis. The aneurysm often causes a tear in the aorta, known as an aortic rupture, which requires immediate attention. Symptoms of a mycotic aneurysm may include:
- Increased white blood cell count
- Severe back pain
- Severe abdominal pain
- Difficulty breathing
- Decreased kidney function
When the condition occurs due to an infection of an aortic graft, symptoms may vary depending on how recently the procedure occurred. When the infection develops within four months, the graft-procedure symptoms may include:
- Increased white blood cell count
- Infection at the entry site (often the groin)
- Graft dysfunction
If the infection sets in later than four months after the procedure, symptoms are often less noticeable and may include:
- A false aneurysm (a collection of blood outside the blood vessels)
- Swelling of the kidney (hydronephrosis)
- An infection in the bone (osteomyelitis)
Causes and Risk Factors
The condition is rare and is caused by an infection in the aorta. The infection can develop due to the presence of bacteria after an aortic graft or bacteria originating in another area and traveling to the aorta through the bloodstream. A history of having an aortic graft increases the risk of developing an infection.
Diagnosis of aortic infection generally begins with the physician taking a medical history and performing a physical examination. The medical team may use one or more diagnostic imaging tests along with examining samples to determine if an infection is present.
A CT scan is the most commonly used diagnostic tool. However, when the condition is caused by an infected aortic graft and occurs soon after surgery, it may be difficult to distinguish changes in the area that are related to the surgery and changes in the area that are due to infection. A CT scan may be used to guide the physician in removing some of the surrounding fluid, which will be tested to determine if an infection is present. Chest X-rays may also be used to diagnose an infection.
An MRI may be used to view the affected area. This diagnostic tool can also show if the aorta has ruptured, or if there is inflammation in the area. During the physical exam the physician will listen to the patient's heart, lungs and abdomen using a stethoscope to see if there is any abnormal rhythm in the heartbeat.
Other laboratory tests, such as blood tests, are often performed to determine the white blood cell count or to rule out other conditions.
Because an aortic infection can have life-threatening complications such as an aortic rupture, treatment is usually needed immediately. Antibiotics are given to the patient to help the body fight off the bacteria that is causing the infection. Surgery to restore normal blood flow, a procedure known as revascularization, is also a common treatment for the condition.
Antibiotics are often the first treatment provided to the patient. If the medical team knows the exact bacteria causing the infection, specific antibiotics will be prescribed. In some cases, the type of bacteria is unknown or there is more than a single type present and a general antibiotic medicine may be prescribed. In some cases, if a patient is unable to have surgical treatment, antibiotic medicine may be used as a long-term treatment option.
When surgery is an option, the type of surgery performed will depend on how severe the infection is and what damage it may have caused to the aorta. For milder cases, a procedure known as in situ revascularization may be performed. During this surgery the damage to the aorta is repaired at the location. The repair may include a new graft if the condition is at an infected graft site. If the patient's condition is more severe, an extra-anatomic surgical procedure may be performed. This involves rerouting the blood vessels to avoid the damaged area while still supplying blood to the areas that need it (bypass).
The knowledgeable and highly trained staff at the Cedars-Sinai Heart Institute will work with each patient to determine the best treatment option.