What are a few of the broad differential diagnoses for this appearance?
Cardiac enlargement (e.g cardiomyopathy), pericardial effusion, anterior mediastinal mass (e.g. thymic tumour - unlikely).
What does splaying of the carina imply?
Enlargement of the pericardial sac in the region of the left atrium - not expected if this represented an anterior mediastinal mass.
Chest x-ray demonstrates a markedly enlarged cardiac silhouette with splaying of the carina.