Asymptomatic Cardiac Mass–Thrombosed Aneurysm of a Coronary Fistula

Abstract

A 33-year-old female was noted to have a systolic murmur during anaesthetic review prior to surgery for ectopic pregnancy. Transthoracic echocardiography suggested an encapsulated immobile spherical right atrial mass suspicious of myxoma. Left ventricular systolic function and valvular structures were normal. Low dose cardiac computed tomography (CT) revealed a large (57 × 23 × 26 mm) mass in the epicardial tissue plane with focal calcification, superposterior to the right atrium, posterior to the aorta and superior vena cava, inferior to the right pulmonary artery and anterior to the left atrium. The largest calibre branch of the dilated left main was a dilated branch of the proximal circumflex which supplied the mass, suspected to be a thrombosed aneurysm of coronary-cameral fistula. This was confirmed on cardiac MRI angiography. The coronary arteries were otherwise normal. Cardiac MRI performed subsequently confirmed CT findings and further demonstrated low to intermediate signal intensity with some heterogeneity within the body of the mass with no definite fat and absence of first pass or delayed perfusion. There was no delayed enhancement. Diagnosis was changed to thrombosed aneurysm of a coronary fistula. Given increased thromboembolic risk, coronary angiography to assess drainage of the mass will be arranged. This case illustrates the incremental value of cardiac CT and cardiac MRI compared to echocardiography in identifying cardiac masses and elucidating their relationship to surrounding structures.