Myocarditis on ¹⁸FDG-PET imaging

Myocarditis is the inflammation of the heart muscle with various clinical presentations and etiology. In this case, we demonstrate the utility of Fluorodeoxyglucose PET scan in identifying its etiology. A 28-year-old female with a history of undifferentiated connective tissue disease and sacroiliitis referred to the cardiology clinic for palpitations. Her symptoms started 3 years ago, were episodic, associated with fatigue, and impaired quality of her life. A resting electrocardiogram revealed sinus tachycardia. Medical workup for sinus tachycardia was unremarkable. Given suspicion for idiopathic myocarditis, a FDG PET using F18 was ordered and revealed diffuse myocardial uptake suggestive of myocarditis. Normal LV systolic function was noted on the echocardiogram. Her tachycardia was successfully treated with ivabradine and diltiazem. She was started on mycophenolate mofetil for myocarditis with improvement in symptoms of tachycardia and fatigue. A repeat FDG PET in follow-up revealed less diffuse uptake with the initiation of therapy. FDG-PET may add value in patients with inappropriate sinus tachycardia found especially if suspicion of underlying connective tissue disease exists. As illustrated in this case, a timely diagnosis could change management decisions as well as significantly impact the quality of life.