Proteus Mediastinitis Causing Fatal Pseudoaneurysm following Aortic Valve Replacement

Area of Science:

• Cardiovascular Surgery
• Infectious Diseases
• Medical Imaging

Background:

• Mediastinitis is a rare but serious complication following cardiac surgery.
• Gram-negative bacterial infections, particularly Proteus mirabilis, can cause late-onset mediastinitis.
• Aortic valve replacement via median sternotomy carries inherent risks of surgical site infections.

Purpose of the Study:

• To report an unusual case of late-onset Gram-negative mediastinitis after aortic valve replacement.
• To highlight the diagnostic challenges and potential fatal outcomes of this rare complication.
• To emphasize the importance of considering remote site infections in post-cardiac surgery patients.

Main Methods:

• Case report detailing a patient's presentation two months post-aortic valve replacement.
• Inclusion of diagnostic imaging findings, specifically Computerised Tomography (CT) scans.
• Analysis of microbiological data from blood cultures and wound discharge.

Main Results:

• The patient developed septic shock with a discharging sternal wound and Proteus mirabilis bacteremia.
• CT imaging revealed a large anterior mediastinal abscess and an aortic pseudoaneurysm.
• The aortic pseudoaneurysm ruptured, leading to a fatal outcome.

Conclusions:

• Late-onset Gram-negative mediastinitis is a rare complication of cardiac surgery, often presenting after initial recovery.
• Proteus mirabilis can cause severe mediastinal infections and associated vascular complications.
• Computerised Tomography is crucial for identifying mediastinal abscesses and pseudoaneurysms in suspected cases.