Cardiac sarcoidosis

Cardiac sarcoidosis (CS) is myocardial granulomatous inflammation, part of the systemic disease sarcoidosis, that can cause heart block, ventricular arrhythmia, or heart failure, often before it is suspected clinically. Because endomyocardial biopsy has poor sensitivity (patchy involvement), imaging plays a central diagnostic and monitoring role.

The 2017 joint SNMMI-ASNC expert consensus document describes a two-part cardiac PET protocol: a resting myocardial perfusion scan (with N-13 ammonia or Rb-82, or a SPECT perfusion tracer where PET perfusion is unavailable) to map blood flow, followed by F-18 FDG PET after patient preparation (prolonged fasting and a high-fat, low-carbohydrate diet, sometimes with heparin) to suppress normal myocardial glucose use and reveal focal inflammatory FDG uptake. The perfusion and metabolism images are read together: a perfusion defect with matched reduced FDG uptake suggests scar, a defect with FDG uptake mismatch suggests active inflammation superimposed on damaged tissue, and normal perfusion with focal FDG uptake suggests early active disease without fixed damage.

F-18 FDG itself is outside this cardiac-agents file (it is a general oncology and inflammation tracer elsewhere in the corpus); the tracers recorded here contribute the perfusion half of the CS protocol, which is required at baseline and at follow-up scans alongside the FDG study.