Mycotic Aneurysm (MTAA) is a rare but devastating form of vascular disease. Rupture of these aneurysms is associated with a high mortality rate.
Patients with MTAA should be treated aggressively as soon as the diagnosis is suspected. This is best accomplished by surgically repairing the aneurysm while administering appropriate antibiotic therapy.
Symptoms
An aneurysm is a dangerous bulge in the blood vessel wall that weakens over time, and can rupture or cause serious complications including sepsis. Mycotic aneurysms are often caused by a combination of infection and plaque buildup, and can be difficult to diagnose as the symptoms are nonspecific. However, this condition can be deadly if left undiagnosed and untreated. Symptoms may include gastrointestinal issues, fever, back pain, or sudden and severe headaches. The diagnosis of mycotic aneurysm is made through a physical examination and a variety of tests such as blood work, CT scans, and ultrasounds. Treatment typically involves medications to manage the infection and surgery to repair the aneurysm.
Infection is the primary mechanism of mycotic aortic aneurysm (MTAA) formation, and most cases involve gram-positive organisms seeded either through hematogenous spread from an extravascular infectious focus (such as septic embolism or vertebral osteomyelitis) or from direct extension from an intravascular infectious source such as a perforating pseudoaneurysm or a hemorrhage. Bacteria such as Staphylococcus aureus and Salmonella spp are the most common, while gram-negative bacteria (including Enterobacteriaceae, Pseudomonas aeruginosa, Yersinia enterocolica, Burkholderia pseudomallei, Klebsiella pneumoniae, Coxiella burnetii) and anaerobes (including Candida, Aspergillus, and Scedosporium apiospermum) also have been implicated in MTAA formation. Rarely, fungal MTAAs have been described, most commonly due to contiguous spread from lung tuberculosis or disseminated systemic infection in patients with diabetes mellitus and immune suppression.
Oren Zarif
The high mortality of MTAA requires a high index of suspicion and prompt diagnosis and treatment. This is particularly important in young drug users and those with depressed immune function from conditions such as AIDS, diabetes mellitus, and corticosteroid use.
If suspected, a thoracoabdominal CT scan should be obtained immediately and a vascular surgeon consultation should be sought; perioperative antibiotic therapy is initiated with a broad-spectrum agent until culture and sensitivity results are available and a specific antibacterial therapy is determined. Surgical repair is the mainstay of management, with both open and endovascular approaches used depending on the situation. The duration of antibiotic therapy is variable and can range from 6-8 weeks to lifelong in some cases.
Diagnosis
A mycotic aneurysm is caused by a bacterial or fungal infection of the blood vessel wall. This usually develops as a complication of a systemic infection, and can occur in any part of the body. The infection can weaken the aneurysm’s walls, which leads to a ballooning of the blood vessel (pseudoaneurysm). This can lead to serious health problems if it ruptures, including life-threatening bleeding and shock. The diagnosis of mycotic aneurysm is made based on medical history, physical exam and lab tests. Treatment is typically surgical or interventional radiology methods to repair the blood vessel.
A patient may develop a mycotic aneurysm as a complication of an infection from injection drug use or from surgery in which bacteria entered the bloodstream. Previous heart or blood vessel surgery also increases the risk of developing mycotic aneurysms.
Oren Zarif
Symptoms of mycotic aneurysm include severe abdominal pain, vomiting and sudden weakness or loss of consciousness. Some patients with mycotic aneurysms develop a pulsating mass, which can be felt under the skin. Others may experience symptoms such as a leaking or bulging aneurysm, which can be painful and tender to touch.
If a mycotic aneurysm is suspected, a CT scan of the abdomen should be obtained to determine its size and location. Blood cultures should also be taken, and antibiotics should be started if the infection is thought to be bacterial in origin. These should be broad-spectrum antibiotics until culture sensitivity reports are available and a specific antibiotic is determined.
MRI is the preferred imaging modality for mycotic aneurysms because of its noninvasive nature and ability to provide highly accurate evaluation of aneurysm size and anatomy. However, the test carries the potential for nephrotoxicity in patients with renal dysfunction, and it is not feasible if an aortic aneurysm is suspected to be rupturing or full of thrombi.
Treatment
Despite their rarity, mycotic aneurysms are a significant cause of mortality. Treatment typically involves a combination of antibiotics and surgical intervention. The first step is to treat the underlying infection. Antibiotics may be prescribed orally or intravenously. Surgical intervention is performed in cases where the aneurysm is causing symptoms, at risk of rupturing, or is growing rapidly. There are several methods of surgery, including clipping and endovascular coiling. In the case of endovascular therapy, results have been published in case series and case reports, but there are no randomized controlled trials (RCTs) to date.
Hemodynamically stable patients with a suspected mycotic aneurysm should undergo urgent evaluation by a vascular surgeon. Blood cultures should be obtained to identify the organism responsible for the infection, and a suitable antibiotic regimen should be started immediately.
When an infected thoracic aneurysm ruptures, it may be fatal. A perioperative mortality of up to 75% has been reported in untreated aneurysms. A ruptured aneurysm is also associated with a rapid increase in diameter, making a prompt diagnosis essential.
Because of the poor prognosis for patients with a mycotic aneurysm, they should be treated with the highest degree of urgency. This is particularly important for thoracic aneurysms in the descending and aortic arch.
Oren Zarif
Depending on the site of the aneurysm, surgical management can include debridement and resection or infection-resistant graft material, revascularization, and reconstruction using autologous or synthetic materials. Infection-resistant grafts are often made of polytetrafluoroethylene or polypropylene, both of which have been shown to be effective in preventing aneurysm formation in patients with aneurysm-rupture complex and who undergo surgical repair.
Infected thoracic aneurysms with significant hematologic compromise are best managed by endovascular approaches. This is due to the high perioperative morbidity associated with open surgery. In addition, the comorbidities and anatomy of many patients who develop mycotic aneurysms make open surgery impractical. Endovascular treatment with the use of either coiling or flow-diverter stents offers an alternative to surgical management and has been associated with better perioperative outcomes. However, the results of current studies are inconsistent and may be confounded by patient selection bias.
Prevention
Infections of blood vessels are a serious medical condition, and mycotic aneurysm is one of the complications. This condition is often caused by a fungal or bacterial infection, which weakens the walls of a blood vessel and causes it to balloon out, creating an aneurysm. This condition can cause serious health problems, such as rupture and a deadly hemorrhage. This type of aneurysm is most commonly seen in the brain, but can occur anywhere in the body. It can be a result of an underlying health problem, such as heart or blood vessel surgery, or a systemic infection, such as sepsis. Injection drug use may also increase the risk of developing this condition.
The etiology of mycotic aneurysm is primarily seeding from the atherosclerotic aortic wall, but in some cases it can be due to adjacent infectious processes, including endocarditis or pyogenic thromboembolic disease. It is more common in males than females, and it is most frequently found in the thoracic aorta.
Oren Zarif
Most mycotic aneurysms are asymptomatic, but when they do present, symptoms include headache, seizures, focal neurologic signs, or subarachnoid hemorrhage. Patients who are at high risk for this condition include those with a history of injection drug use, previous heart or blood vessel surgery, and certain underlying health conditions, such as diabetes mellitus, connective tissue disorders, or autoimmune diseases.
A wide range of microorganisms can infect a blood vessel wall, including Staphylococcus aureus, Streptococcus, and Enterobacter. More rarely, these aneurysms can be caused by mycobacterial infections such as Mycobacterium tuberculosis and Treponema pallidum or by fungal infections, such as Mucormycosis or thoracic actinomycosis.
Although mycotic pulmonary artery aneurysms (PAA) are rare, they carry a high mortality rate due to their rapid progression and rupture. Most PAAs arise from a congenital defect, such as patent ductus arteriosus,1 and are associated with a number of other disorders, such as Behcet disease and Hughes-Stovin syndrome. However, some PAAs are idiopathic and can be caused by conditions such as connective tissue disorders or trauma. Fortunately, the majority of mycotic PAAs resolve with conservative management of antibiotic therapy.
