An aortic root abscess is a serious complication of infective endocarditis and most commonly seen in patients who have had aortic root repair and/or aortic valve replacement.
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Epidemiology
Aortic root abscess occurs as a complication of infective endocarditis in 10-37% 9. Abscess formation in post-surgical patients (aortic root repair and/or aortic valve replacement) is most commonly encountered in the first 5 years following surgery, most of which occur in the first 2 years.
Clinical features
Fever is almost universal in patients with aortic root abscess. Patients may also present with a new or changing murmur, valvular dehiscence, weight loss, poor appetite, systemic embolisation, or features of congestive heart failure.
Pathology 2
Early abscessation occurs within the first 2 months of surgery and is usually caused by perioperative contamination such as from skin, wound or prostheses. Staphylococcus epidermidis and S aureus the most frequent causative pathogens.
Late abscessation occurs greater than 2 months following surgery and resembles native valve endocarditis. Streptococci species are the most common causative pathogens.
In mechanical valves, infection starts at the sew line and extend around the valve. In bio-prosthetic valves, infection resembles infective endocarditis of the native aortic valve where infection is limited to the cusps. The sewing cuff is rarely involved and periprosthetic abscesses are uncommon.
Radiographic features
General
Abscesses tend to be saccular in shape, range from 1-3 cm in diameter. Depending on the sinus of origin, they may extend beneath the pulmonary trunk, right pulmonary artery, interventricular septum or mitral annulus.
Echocardiography
Transoesophageal echocardiography is significantly more sensitive for the detection for perivalvular abscesses than transthoracic imaging, although both have high specificity 14.
The typical sonographic appearance is that of a perivalvular echolucent area, most commonly located in the aortomitral curtain (i.e. the intervalvular fibrosa). Early involvement may be subtle, manifesting as a thickening of the aortic root 15. There should be an absence of colour flow Doppler signal within the abscess, the presence of which may imply the formation of a pseudoaneurysm or fistula.
CT / CT angiography
Perivalvular abscesses on CT can appear as a collection of fluid attenuation around the aortic valve surrounded by inflammatory tissue with peripheral contrast enhancement. An abscess can spread into surrounding structures, such as the interatrial septum or left ventricular myocardium.
Locules of gas may additionally be present in some cases. Phlegmon is represented by a thickened area around the aortic root 2. Pseudoaneurysms fill with contrast. An adjacent pericardial effusion may be present.
CT also show complications such as fistula formation.
Some authors suggest an additional delayed phase (at approximately 70 seconds) in cases where there is high clinical suspicion of infection-related complications, such as pseudoaneurysm or fistula formation 11.
Nuclear medicine
Hybrid imaging with Gallium-67 SPECT may complement workup 4.
Treatment
Patients can be managed with IV antibiotics alone but the prognosis is much greater when revision valve replacement and/or root repair is combined with IV antibiotics.
Complications
valve destruction and/or dehiscence
arrhythmias
-
fistulation
into the mitral annulus
aorta
-
cardiac chambers e.g.
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