Mycotic aneurysm

Mycotic aneurysm is an aneurysm that results from an infectious process that involves the arterial wall.^[1] A person with a mycotic aneurysm has a bacterial infection in the wall of an artery, resulting in the formation of an aneurysm. The most common locations include arteries in the abdomen, thigh, neck, and arm. A mycotic aneurysm can result in sepsis, or life-threatening bleeding if the aneurysm ruptures. Less than 3% of abdominal aortic aneurysms are mycotic aneurysms.^[2]

William Osler first used the term “mycotic aneurysm” in 1885 to describe a mushroom-shaped aneurysm in a patient with subacute bacterial endocarditis. This may create considerable confusion, since “mycotic” is typically used to define fungal infections. However, mycotic aneurysm is still used for all extracardiac or intracardiac aneurysms caused by infections, except for syphilitic aortitis.^[3] The term “infected aneurysm,” proposed by Jarrett and associates^[4] is more appropriate, since few infections involve fungi.^[5] According to some authors, a more accurate term might have been endovascular infection or infective vasculitis, because mycotic aneurysms are not due to a fungal organism.^[6]

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Salmonella ^[7]
• Staphylococcus aureus ^[7]
• Staphylococcus epidermidis
• Streptococcus pneumoniae

Mycotic aneurysms account for 2.6% of aortic aneurysms.^[3] For the clinician, early diagnosis is the cornerstone of effective treatment. Without medical or surgical management, catastrophic hemorrhage or uncontrolled sepsis may occur. However, symptomatology is frequently nonspecific during the early stages, so a high index of suspicion is required to make the diagnosis.^[5]

Intracranial mycotic aneurysms (ICMAs) complicate about 2% to 3% of infective endocarditis (IE) cases, although as many as 15% to 29% of patients with IE have neurologic symptoms.^[6]

• Empiric antimicrobial therapy^[8]

• Preferred regimen: Vancomycin 15 mg/kg IV divided q12h (trough of 15-20 mcg/mL) for 6 weeks AND (Ceftriaxone 2 g IV q24h for 6 weeks OR Piperacillin-Tazobactam 3.375 g IV q6h for 6 weeks OR Ciprofloxacin 400 mg IV q12h for 6 weeks)
• Note: For critically ill patients, start with a vancomycin loading dose of 25 mg/kg.

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