Aortic prosthetic valve endocarditis as an incidental finding on abdominal CT

A 78-year-old woman with a history of severe aortic valve stenosis, who underwent surgical valve replacement with a sutureless bioprosthesis 15 months previously (Figure 1), was admitted to our emergency department presenting with weight loss, night-time sweats, severe asthenia and right iliac fossa pain. Due to abdominal symptoms, an abdominal CT was performed.

- Abdominal CT on admission: Inflammatory changes in the perivalvular and epicardial fat together with a phlegmon surrounding the partially included aortic valve bioprosthesis (Figure 2). Multiple hypodense splenic subcapsular lesions, consistent with septic emboli (Figure 3). These findings suggested prosthetic valve endocarditis and further specific studies were performed. 

- Transesophageal echocardiography three days later: leaflet thickening of the aortic bioprosthesis and formation of a pseudoaneurysm of the aortic root, consistent with complicated infective endocarditis (Figure 4). 

- Cardiac CT eleven days later: severe thickening of the prosthetic leaflets with multiple vegetations (Figure 5). Compared with the images of the initial abdominal CT, an increase of the inflammatory changes was seen, with the formation of a periprosthetic abscess (Figure 6). A periprosthetic pseudoaneurysm was confirmed, seen as a contrast-filled saccular formation in the right posterolateral aspect of the aortic root (Figure 8). In addition, another pseudoaneurysm was seen in the anterior wall of the aortic arch, suggesting a probable embolic origin (Figure 9).

Infective endocarditis (IE) is an entity with a prevalence of 3-9 cases/100.000 people, affecting more predominantly patients with prosthetic valves and other intracardiac devices, previous IE and congenital heart disease.

 In the pathogenesis, there is an endocardial injury with an associated period of bacteremia which allows the microorganisms to adhere to the injured endocardial surface [1].

Prosthetic valve endocarditis (PVE) accounts for over 20% of all IE, being Staphylococcus aureus the main pathogenic cause [2].

The clinical presentation is non-specific and it should be considered in any patient with high risk presenting with sepsis of unknown origin or fever. 

The modified Duke criteria, and the European Society of Cardiology (ESC) 2015 modified diagnostic criteria include [3,5]:

1- Microbiological findings: Positive blood cultures and microorganism identification positive for IE.

 2- Imaging findings:

Echocardiography is central to diagnosis and follow-up, however, cardiac CT has demonstrated to be equivalent or superior to echocardiography in the diagnosis and detection of complications, especially in PVE, as well as on the preoperative management [4]. CT may also be useful to define the size, anatomy and calcification of the aortic valve, aortic root and ascending aorta [5]. Therefore, ESC guidelines introduced cardiac CT findings as major imaging criteria [5,6].

The main imaging signs in cardiac CT are [7]:

• Vegetations: mobile soft-tissue lesions attached to the valvular leaflets or to any endocardial surface or device.
• Leaflet perforation: small defects in the leaflet that allow retrograde blood flow into the preceding cardiac chamber.

It is also crucial  to identify the perivalvular extension, affecting 56-100% of patients with PVE, and a frequent reason for uncontrolled infection [5,8]:

• Abscesses: low attenuation collections that do not communicate with the cardiovascular lumen.
• Pseudoaneurysms: perivalvular fluid collections that do communicate with the cardiovascular lumen and appear as a pulsatile contrast filled areas on dynamic cine ECG-gated CTA.
• Fistulas: extension of abscesses/pseudoaneurysms to adjacent cavities (usually aorto-cavitary) and communication between them.
• Prosthetic dehiscence: dislocation of the valvular prosthesis from its original location. 

The management of IE includes a long period of antibiotic treatment associated with surgery in patients who undergo heart failure, uncontrolled infection or in order to prevent embolism [3]. 

It is often associated with high mortality (around 20%), rising up to 50% in cases of PVE [3]. The patient we present had blood cultures positive for Streptococcus Gallolyticus penicillin sensitive. She did not fulfill surgical criteria, and died 40 days after the diagnosis.

 Written informed patient consent for publication has been obtained.