Multisystem granulomatous disease
Unknown etiology
Results in arrhythmias, HF and SCD
Second leading cause of sarcoidosis-related mortality
- #1 is pulmonary
Increasing prevalence? Or are we just doing better with diagnosis?
Diagnostic uncertainty is common
- Yield of EMB isn’t high b/c disease often patchy
Risk stratification is challenging

Diagnosis

FDG-PET

Assess disease activity and monitor therapy response
Whole body PET can identify extracardiac biopsy sites
Mismatch in perfusion and metabolism is highly specific (100%, 83% sensitive)
Any FDG uptake pattern specificity can be as low as 33%
Patient preparation is key 🔑
- It has to be endogenous ketosis, i.e. by fasting (KEE-TOSIS study)
- - Highlights that sometimes longer fasting yields better results (even if you have to go to 72 hours!)
Must rule out ischemic heart disease
- b/c ischemic cells with take up FDG, which can be misleading. Ischemia induces translocation of GLUT4 to cell membrane

Figure source

Limited whole-body PET study using the same 18F-FDG injection should be performed in addition to the dedicated cardiac 18F-FDG study
Should include the chest, liver, and spleen
Can be interpreted even if poor dietary preparation or non-cardiac protocol
SUV of index nodes should be measured
CT for AC can assess presence of LAD

CMR has a high NPV, so obtain CMR only in low clinical suspicion. Obtain CMR and PET when high clinical suspicion

No preparation is needed
May identify other causes of cardiomyopathy
Ideally obtained at baseline, prior to PPM/ICD
If PPM is present, artifact tends to be minimal
If ICD is present, artifact tends to be significant, and results are less accurate. Use wide band imaging and lift device as high as possible.

Interpretation with MRI:

T1/2 mapping, T2-weighted edema imaging and LGE are most important sequences
LGE carries the strongest prognostic value
95% sensitivity, 85% specificity
Typical pattern: multifocal multi-pattern LGE with septal and RV involvement. More specific but no pattern is 100% specific.