Incidental Finding of a Giant Left Main Coronary Artery Aneurysm as an Anterior Mediastinal Mass

A 79-year-old female with a history of hypertension, diabetes, and chronic kidney disease presented to the emergency department with an acute asthma exacerbation and was incidentally found to have a large anterior mediastinal mass on a chest X-ray (Figure 1A ). The mass was further evaluated on a coronary computed tomography angiography (CCTA) which identified a giant 6.8x5.7x7.0 cm coronary artery aneurysm (CAA) located at the bifurcation of the left main coronary artery (LMCA), involving both the proximal left anterior descending and circumflex coronary arteries. There was mild coronary atherosclerosis with minimal stenosis of <25% in the mid-left anterior descending artery. Moderate mixed calcified and non-calcified thrombus was noted in the coronary artery (Figure 1B-C, Supplementary Materials; Movies I-II). The patient did not have any prior coronary angiography or coronary instrumentation. The patient remained asymptomatic with no exertional chest pain or dyspnea. The electrocardiogram showed normal sinus rhythm and laboratory studies revealed normal high-sensitivity troponin I levels. A transthoracic echocardiogram demonstrated normal LV ventricular size and systolic function. The patient underwent cardiac catheterisation which confirmed the giant LMCA aneurysm, with no other obvious coronary pathology (Figure 1D, Supplementary Materials; Movie III). Given her co-morbidities, age, and lack of symptoms, the LMCA aneurysm was managed conservatively with dual antiplatelet therapy with aspirin and clopidogrel.