The value of F-18 FDG PET-CT scan in the diagnosis of infection of unknown origin in a patient with aortic valve replacement. in the diagnosis of infection of unknown origin in a patient with Aortic valve replacement. value of F-18 FDG PET/CT scan in the diagnosis of infection of unknown origin in a patient with Aortic valve replacement.

Objectives: The authors present a case study of a patient with recurrent fevers and sepsis from an infection of unknown origin.

Methods: The patient was a 51-year-old female presenting with a fever of unknown origin. The patient had been having recurrent fevers and hospitalizations for sepsis. On the current admission the patient was found to have positive blood cultures for Streptococcus Viridans. The patient had a past medical history for aortic stenosis with a mechanical valve replacement in 2005 and a revision with a bioprosthetic valve in 2011 after sustaining a subdural hemorrhagic stroke on warfarin. A transthoracic echo was obtained, which showed thickening of the bioprosthetic valve leaflets and normal physiological regurgitation, no evidence of an abscess was seen. Two follow-up transesophageal echocardiograms were obtained for further evaluation, these studies showed an echolucency around the valve without evidence of vegetation’s and presumed to be ectasia/aneurysm or hematoma. With the persistent fever and positive blood cultures an Indium-111 WBC scan was ordered for further evaluation of the echolucency around the bioprosthetic heart valve, which was read as showing mild diffuse activity with no abnormal focal increase in radiotracer activity in the region of the aortic valve. Clinical suspicion persisted and an F-18 FDG PET/CT of the chest was ordered, which showed intense radiotracer activity in the posterior aspect of the aortic valve correlating to the area of echolucency identified on transesophageal echocardiogram. Additional findings showed increased radiotracer activity in the aorta correlating to calcifications, which was presumed to be inflammation and right hilar uptake which was deemed due to granulomatous disease.

Results: The patient was taken to the operating room for a third aortic valve replacement. The procedure identified a large abscess at the annulus of the left coronary cusp. During the procedure significant separation of the outflow tract of the left main was identified and repaired with a bovine patch. The valve was again replaced with a bioprosthetic and a bovine patch using Nicks procedure. Weaning from cardiopulmonary bypass was complicated and required an intraaortic balloon pump, which the patient was eventually weaned from. After weaning from cardiopulmonary bypass the patient continued to deteriorate and expired.

Conclusion: This case illustrates the value of F-18 FDG PET/CT in the diagnosis of and localization of a periaortic valve abscess in a patient with multiple valve replacements, recurrent fevers/sepsis and inconclusive imaging with transthoracic echocardiogram, transesophageal echocardiogram and Indium-111 WBC scan. The localization of the FDG activity to the posterior aspect of the valve which corresponded to the findings on transthoracic echocardiogram was key. Research Support: