PO-01-087 A RARE CASE OF BI-ATRIAL FDG-UPTAKE: PRESENTING AS NEW ONSET ATRIAL FIBRILLATION

Abstract

Isolated atrial myocarditis is rare, with presenting symptoms that are non-specific. Prior reports have suggested association with atrial arrythmias and increased risk of stroke due to atrial dysfunction. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) CT scan is considered as a goal standard test for the diagnosis of myocarditis. To present a case highlighting that isolated atrial myocarditis had higher incidence atrial arrythmias and oral anticoagulation should be considered in such cases. N/A A 55yo male with no prior medical history presented with non-specific symptoms of fatigue, shortness of breath and frequent palpitations. He underwent 2D echocardiogram showed LVEF of 50-55% with mild bi-atrial dilatation with no regional wall motion abnormalities and was diagnosed with incidental atrial fibrillation during the procedure. He was referred to cardiac electrophysiology for further work up. During his initial EP clinic visit, 12 lead ECG demonstrated normal sinus rhythm with premature atrial contractions and premature ventricular contractions. Due to symptomatic, dual chamber arrythmias, cardiac MRI (CMR) and FDG-PET CT was ordered to rule out myocarditis. The CMR was negative for any LGE however, high-fat dietary preparation FDG-PET CT scan revealed uptake on bi-atrial walls (figure) and interatrial septum with SUV max of 3.1. There was no LV myocardial FDG uptake noted. Patient was diagnosed with isolated atrial myocarditis and was started on dronedarone, OAC (CHADS2VASc =0) for stroke prophylaxis and immunosuppressive therapy (methotrexate and low dose prednisone). Invasive atrial myocardial biopsy was not considered due good response to therapy. Isolated atrial myocarditis is an uncommon presentation of acute myocarditis and is associated with atrial arrythmias. FDG PET-CT or CMR imaging may be useful to aid diagnosis. Long-term response to immunosuppressive therapy may need further investigations. OAC should be considered for stroke prophylaxis, despite low CHADS2VASc due to unknown long-term implications of atrial dysfunction.