Case of isolated cardiac sarcoidosis diagnosed by newly developed abnormal uptake during serial follow-up fluorine-18 fluorodeoxyglucose positron emission tomography

Abstract

Cardiac sarcoidosis (CS) causes lethal arrhythmia and heart failure and has a poor prognosis; therefore, early detection and early stage treatment are important. However, diagnosis of isolated CS may be difficult in some cases owing to the low sensitivity of myocardial biopsy. Herein, we describe the case of a patient with isolated CS, showing change from negative to positive fluorine-18 fluorodeoxyglucose (¹⁸ F-FDG) positron emission tomography (PET) uptake results within 9 months. The patient showed rapid reduction in left ventricular systolic function with sustained ventricular tachycardia. The diagnosis of isolated CS is often under-recognized in clinical practice because it commonly requires the diagnosis of extracardiac disease in the absence of a positive endomyocardial biopsy. The Japanese Circulation Society recently published guidelines for CS diagnosis stating that isolated CS can be clinically diagnosed with positive ¹⁸ F-FDG PET or ⁶⁷ Gallium result. In this case, serial follow-up ¹⁸ F-FDG PET was useful for diagnosing isolated CS.

Keywords: FDG-PET; Isolated cardiac sarcoidosis; MRI.

Figure 1

First screening echocardiography of parasternal long axis view. Basal thinning of interventricular septum (white arrow) and aneurysm of posterior (yellow arrow) are shown. Cardiomegaly with preserved left ventricular ejection fraction (56%) was observed.

Figure 2

Cardiac magnetic resonance imaging showing midwall late gadolinium enhancement (LGE) of basal interventricular septum and subendocardial LGE in the posterior and lateral wall of the left ventricle. Fused images clearly show an overlap of ¹⁸F‐FDG uptake and LGE in most myocardial regions. Follow‐up ¹⁸F‐FDG PET showed increased ¹⁸F‐FDG uptake in most myocardial regions, but LGE positive regions remained unchanged. However, there was a discrepancy among the areas of ¹⁸F‐FDG uptake and LGE in the basal inferior wall (white head arrows). ¹⁸F‐FDG PET, fluorine‐18 fluorodeoxyglucose positron emission tomography.

Figure 3

Chronological changes of ¹⁸F‐FDG PET findings and biomarkers in baseline and after 9 months (A and D, full body; B and E, enlarged view of the thorax; and C and F, transaxial fusion PET/computed tomography findings). Baseline images revealed no abnormal ¹⁸F‐FDG uptake including the heart. However, follow‐up ¹⁸F‐FDG PET demonstrated focal ¹⁸F‐FDG uptake (red arrows) in the posterior and lateral wall of the left ventricle. ¹⁸F‐FDG PET, fluorine‐18 fluorodeoxyglucose positron emission tomography; SUV, standardized uptake value.

Figure 4

Electrocardiography on admission showing wide QRS tachycardia of 160 beats per min. QRS complex showed a right bundle block pattern and inferior axis, suggesting posterior and lateral wall of left ventricular origin.