Is positron emission tomography enough to rule out cardiac sarcoidosis? A case report

BACKGROUND: Cardiac sarcoidosis (CS) is associated with poor prognosis, yet the clinical diagnosis is often challenging. Advanced cardiac imaging including cardiac magnetic resonance (CMR) and positron emission tomographic (PET) have emerged as useful modalities to diagnose CS. CASE SUMMARY: A 66-year-old woman presented with palpitations. A 24-h Holter monitor detected a high premature ventricular contraction burden of 25.6%. She underwent two transthoracic echocardiograms; both showed normal results. Stress perfusion CMR did not show any evidence of ischaemic aetiology; however, myocardial lesions detected by late gadolinium enhancement (LGE) imaging raised suspicion for CS. While there was no myocardial uptake of fluorodeoxyglucose (FDG) in subsequent cardiac PET, high FDG uptake was seen in hilar lymph nodes. Lymph node biopsy confirmed the diagnosis of sarcoidosis. DISCUSSION: Cardiac magnetic resonance and PET imaging are designed to evaluate different aspects CS pathophysiology. The characteristic LGE in the absence of increased FDG uptake suggested inactive CS with residual myocardial scarring.