Although rare, mycotic aneurysms have high rates of morbidity and mortality. The true incidence is not known, but it has been estimated to be between 0.65% and 1.3% of all aortic aneurysms . Furthermore, the incidence of thoracic aortic aneurysm is estimated to be 5.9 cases per 100,000 people/year , making thoracic aortic mycotic aneurysms (TAMAs) even rarer. Mycotic aneurysms were first described by Osler secondary to endocarditis, and the term “mycotic” referred to any type of infection and not just fungal etiology [1,2]. Fungal organisms like Aspergillus species responsible for formation of mycotic aneurysms are rare; more common organisms implicated are Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus, and Salmonella. The incidence of mycotic aneurysms caused by fungi is difficult to ascertain, since there are few reports. The Centers for Disease Control and Prevention estimates the incidence of aspergillosis to be 1 to 2 cases per 100,000 people/year .
Mycotic aneurysms may present with a constellation of nonspecific symptoms and signs, most commonly fever, night sweats, leukocytosis, elevated inflammatory markers, sepsis, anterior chest discomfort, dysphagia, cough, wheezing, stridor, and pneumonitis [3–7]. A high index of suspicion is required to ascertain the diagnosis and implement treatment promptly. Mycotic aneurysms have high rates of rupture and are generally associated with poor outcomes despite medical and surgical intervention [1,2,4–7]. However, better antimicrobial therapies and imaging modalities are helping to ascertain the diagnosis earlier. Past studies have shown that 80% of mycotic aneurysms are the result of microbial aortitis and 3% are estimated to involve infection of a preexisting aneurysm .
A 79-year-old woman underwent aortic valve replacement (AVR) with a bovine bioprosthesis in April 2012. Past medical history included hypertension, paroxysmal atrial fibrillation, and no immunocompromised status. In August 2012 she presented with sudden bilateral loss of vision without fever, chills, or any signs of infection. The most recent echocardiogram showed no issues with the prosthetic aortic valve. However, echocardiogram on admission showed a large vegetation occupying 80% of the ascending aortic lumen together with a large pseudoaneurysm and disruption of the suture line of the aorta (Fig. 1). The Mitroflow® bioprosthetic valve (Sorin Group, Arvada, CO) was working appropriately. Chest computed tomography (CT) scan showed a large pseudoaneurysm, possibly mycotic (Fig. 2). Considering the friable appearance of this mass in the aorta, performing an angiogram was not found to be safe.
In the operating room, the patient was heparinized and cannulated through the left femoral artery and left femoral vein, and placed on cardiopulmonary bypass before opening the chest. Distal control was achieved above the aneurysm (where the aorta was normal) after an uneventful redo sternotomy. The pseudoaneurysm was left intact within its pericardial covering. The patient's temperature was decreased to 28°C. The large mycotic aneurysm was opened, revealing a large fungal ball sitting in the lumen of the aorta. Amphotericin wash was given several times. The Mitroflow® bioprosthetic valve appeared normal. The entire area of the pseudoaneurysm and fungus ball was excised and sent for bacteriology analysis. At this time, a 24 mm homograft was used to replace the ascending aorta. The patient recovered appropriately. Postoperative chest CT was obtained (Fig. 3). The patient exhibited mental status changes on postoperative day 5, which prompted brain MRI. Two cerebellar abscesses and a hemorrhagic stroke were noted (Fig. 4), for which the patient declined treatment. Currently, the patient is doing well, living with her husband, although she did not recover her vision. The patient completed a yearlong antifungal therapy of intravenous amphotericin and oral fluconazole. The last brain MRI showed much improvement (Fig. 5).
We present a rare case of TAMA with an unusual presentation. In the literature, most cases of TAMA caused by fungus have presented with some type of systemic symptom (i.e., fever, tachycardia, hypotension, leukocytosis, etc.) [1,4–7]. Our patient presented with only a complaint of progressive bilateral vision loss. At the time of surgery, the aortic valve prosthesis was intact and free of infection. In our case, the suspected site of infection was the suture line above the valve, possibly a pledgeted suture contaminated in the operating room at the time of aortic valve replacement 20 weeks prior. As alluded to in other case reports, the possible origin of the infective agent in our patient is suspected to be airborne spores arising from the operating room ventilation system. The literature reports an average of 10 months between surgery and diagnosis [5–7]. A high index of suspicion and prompt surgical and medical therapy must be implemented immediately to avoid long-term morbidity and mortality. Traditionally, treatment has included surgical debridement, including graft excision, and aggressive antifungal therapy; however, mortality remains high, attributed to both the highly aggressive nature of the infection and delay in diagnosis. It is important to note that despite intervention, the patient sustained embolic and hemorrhagic strokes preoperatively, and she did not recover her sight; however, she continues to be well otherwise.
In summary, thoracic aortic mycotic aneurysms caused by Aspergillus are a rare but serious entity with high rates of morbidity and mortality, which requires prompt recognition and implementation of medical and surgical therapy.