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Prognostic Value of FDG PET in Endocarditis
Study Questions:
What is the prognosis of patients with left-sided infectious endocarditis who have abnormal 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scans versus those who have normal scans?
Methods:
This was a prospective single-center registry of 173 consecutive patients who had definite left-sided infectious endocarditis conducted at an academic medical center in France. FDG PET was performed after a 12-hour fast and a pre-scan low-carbohydrate, high-fat, high-protein meal. Valvular FDG uptake was considered abnormal when <50% of the valve circumference was involved and could be confirmed on nonattenuation corrected images. Intensity of uptake was graded into three categories: low (less than liver), intermediate (equal or slightly more than liver), or high (far greater than liver). Patients with intense, homogenous myocardial FDG uptake were excluded as nondiagnostic imaging. The primary endpoint was a composite of major adverse cardiac events (MACE) including death, recurrent infectious endocarditis, heart failure, unplanned cardiovascular hospitalization, and new embolic events on antibiotics.
Results:
After exclusions (n = 122 excluded because infection did not involve left-sided valves; n = 65 excluded because imaging was performed >2 weeks after antibiotic initiation; n = 7 excluded for PET image quality). The population included 109 with prosthetic valves (n = 80 with aortic prostheses and n = 29 with mitral prostheses) and 64 with native valve endocarditis. FDG PET was more likely to be abnormal in patients with prosthetic rather than native valve endocarditis (83% vs. 16%, odds ratio, 31; p = 0.0001). C-reactive protein and paravalvular complications were also associated with abnormal FDG uptake (odds ratios, 1.1 and 3.1, respectively; both p < 0.05). False-negative PET occurred in 17% of prosthetic endocarditis patients. PET also frequently found ectopic foci of infection and portal of entry.
At a mean of 225 days, 94 patients experienced MACE. Among prosthetic valve endocarditis, independent predictors of MACE included positive FDG PET/CT (hazard ratio [HR], 2.7; p = 0.04) with added risk associated with moderate to intense FDG uptake (additional HR, 2.3; p = 0.03) as well as C-reactive protein and severe valvular regurgitation. Among patients with native valve endocarditis, FDG PET was not associated with MACE, but was associated with new embolic events (HR, 8.8; p = 0.02).
Conclusions:
Abnormal FDG PET is associated with greater MACE in patients with prosthetic valve endocarditis.
Perspective:
This study adds to a growing body of literature supporting the use of FDG PET for diagnosis and now prognosis in patients with prosthetic endocarditis. The lack of value in patients with native valve endocarditis is concerning and suggests caution be used prior to widespread use of this imaging method in patients without valve prostheses. Optimal pathways for use of this information and whether FDG PET should be used to select patients for reoperation versus medical therapy remains unclear.
Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Valvular Heart Disease, Cardiac Surgery and Heart Failure, Cardiac Surgery and VHD, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Interventions and Imaging, Interventions and Structural Heart Disease, Computed Tomography, Nuclear Imaging
Keywords: Anti-Bacterial Agents, Cardiac Surgical Procedures, C-Reactive Protein, Diagnostic Imaging, Endocarditis, Endocarditis, Bacterial, Fluorodeoxyglucose F18, Heart Failure, Heart Valve Diseases, Heart Valve Prosthesis, Positron-Emission Tomography, Prognosis, Reoperation, Tomography, X-Ray Computed
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