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Impact of FDG PET for Suspected Cardiac Sarcoidosis
Study Questions:
What are the prognostic implications of abnormalities on positron emission tomography (PET) imaging in patients with suspected cardiac sarcoidosis?
Methods:
This was a retrospective analysis of 269 patients referred for PET assessment of possible cardiac sarcoidosis at a single high-volume quaternary center. Patients underwent cardiac PET imaging with rubidium-82 for perfusion and 18F-labeled fluorodeoxyglucose (FDG) for inflammation after a 24-hour preparation with a low-carbohydrate diet and a 12-hour fast. Images were semi-quantitatively scored for perfusion defects and FDG uptake. FDG uptake was also quantified as maximum, minimum, mean, and coefficient of variation across the myocardium. Survival analysis was performed for the composite endpoint of mortality from any cause, heart transplantation, or ventricular arrhythmia requiring defibrillation.
Results:
After a mean follow-up of 1.8 years, 63 patients experienced the composite endpoint. After comprehensive adjustment, segments with perfusion defects and abnormal FDG uptake were associated with adverse outcome (adjusted hazard ratio, 1.12; 95% confidence interval [CI], 1.01-1.24; p = 0.029). Coefficient of variation in FDG uptake was also associated with adverse outcomes (adjusted hazard ratio, 1.05; 95% CI, 1.01-1.10; p = 0.04).
Conclusions:
Findings of mismatch between perfusion and inflammation based on PET, along with heterogeneity of metabolism, are both related to adverse prognosis in patients with suspected cardiac sarcoidosis.
Perspective:
These data add to a growing body of work supporting the use of cardiac PET in diagnosis and management of cardiac sarcoidosis. Importantly, they show that metabolic imaging with FDG alone to identify inflammation is insufficient and perfusion defect assessment is important. In part, this could be due to a high rate of false-positive FDG uptake, particularly when dietary preparation is not rigorously followed. Conversely, the combination of a perfusion defect and concomitant inflammation suggests a low likelihood that this finding is spurious and carries adverse prognosis.
Keywords: Arrhythmias, Cardiac, Cardiomyopathies, Defibrillators, Diagnostic Imaging, Diet, Carbohydrate-Restricted, Fluorodeoxyglucose F18, Heart Failure, Heart Transplantation, Inflammation, Myocardium, Perfusion, Positron-Emission Tomography, Sarcoidosis
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