A Young Woman With Left Atrial Mass
A 37-year-old female patient with a past medical history significant for pulmonary embolism secondary to prothrombin factor II mutation in the setting of oral contraceptive use and pregnancy-induced hypertension presented to the emergency department with a chief complaint of palpitations that worsened with exertion. The palpitations had increased in frequency over the past year; on the day of admission, she was found to have frequent premature atrial contractions and brief runs of atrial tachycardia during telemetry monitoring. Transthoracic echocardiogram revealed a left atrial mass measuring approximately 2.0 cm. Cardiac magnetic resonance imaging (MRI) was subsequently performed and confirmed the presence of a large left atrial mass (3.8 x 1.7 cm) with irregular borders that was invading the left atrial wall and extending into the ostia of the superior pulmonary veins. Tissue characteristics included isointense to myocardium on T1 images, hyperintense on T2 images, significant contrast uptake on first pass perfusion, with heterogeneous contrast uptake by delayed enhancement. No pericardial effusion was seen. See Videos 1 & 2 and Figure 1.
Based on the case presentation and cardiac MRI findings, what is the most likely diagnosis?