FDG MR/PET to Diagnose Cardiac Sarcoidosis

Study Questions:

What is the diagnostic usefulness of hybrid cardiac magnetic resonance (CMR) and positron emission tomography (PET) using 18F-fluorodeoxyglucose (FDG) for active cardiac sarcoidosis (aCS)?

Methods:

Patients with clinical suspicion of aCS underwent hybrid CMR/PET with late gadolinium enhancement (LGE) and FDG to assess the pattern of injury and disease activity, respectively. Patients were categorized visually as magnetic resonance (MR)+PET+ (characteristic LGE aligning exactly with increased FDG uptake), MR+PET- (characteristic LGE but no increased FDG), MR-PET- (neither characteristic LGE nor increased FDG), and MR-PET+ (increased FDG uptake in absence of characteristic LGE) and further characterized as aCS+ (MR+PET+) or aCS- (MR+PET-, MR-PET-, MR-PET+). FDG uptake was quantified using maximum target-to-normal-myocardium ratio and the net uptake rate (Ki) from dynamic Patlak analysis. Receiver operating characteristic methods were used to identify imaging biomarkers for aCS. FDG PET was assessed using computed tomography/PET in 19 control subjects with healthy myocardium.

Results:

A total of 25 patients (12 males; 54.9 ± 9.8 years of age) were recruited prospectively; eight were MR+PET+, suggestive of aCS; one was MR+PET-, consistent with inactive CS; and eight were MR-PET-, with no imaging evidence of CS. Eight patients were MR-PET+ (six with global myocardial FDG uptake, two with focal-on diffuse uptake); they demonstrated distinct Ki values and hyperintense maximum standardized uptake value compared with MR+PET+ patients. Similar hyperintense patterns of global (n = 9) and focal-on-diffuse (n = 2) FDG uptake were also observed in control patients, suggesting physiological myocardial uptake. Maximum target-to-normal-myocardium ratio values were higher in the aCS+ group (p < 0.001), demonstrating an area under the curve of 0.98 on receiver operating characteristic analysis for the detection of aCS, with an optimal maximum target-to-normal-myocardium ratio threshold of 1.2 (Youden index: 0.94).

Conclusions:

The authors concluded that CMR/PET imaging holds major promise for the diagnosis of aCS, providing incremental information about both the pattern of injury and disease activity.

Perspective:

This study reports that hybrid CMR/PET in CS can provide comprehensive assessments of myocardial function, the pattern of injury, and disease activity in a single co-registered scan, as well as information about extracardiac disease, with important potential implications for patient diagnosis and management. This hybrid approach may offer significant potential for improving the diagnostic accuracy of cardiac involvement in sarcoidosis, with important therapeutic implications, and appears better than stand-alone CMR or PET imaging as the imaging modality of choice for CS. Additional studies are needed to confirm these findings.

Clinical Topics: Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Acute Heart Failure, Heart Failure and Cardiac Biomarkers, Computed Tomography, Magnetic Resonance Imaging, Nuclear Imaging

Keywords: Biological Markers, Cardiac Imaging Techniques, Fluorodeoxyglucose F18, Gadolinium, Heart Failure, Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy, Myocardium, Primary Prevention, Positron-Emission Tomography, Sarcoidosis, Tomography, X-Ray Computed


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