The chest x-ray (AP x-ray done in resus area) shows a widened mediastinum with prominent aortic knuckle. The appearance in the context of concerning chest pain should raise suspicion for an aortic dissection. The patient went onto have a CT aortogram which confirmed a Stanford A aortic dissection.

CT images from the same patient –

The patient underwent emergency surgery and survived.

Chest x-ray features are nonspecific in a patient with aortic dissection. Following abnormalities could be present.

• Mediastinal widening.
• Double aortic knob sign.
• Enlarged aorta with poorly defined aortic contour.
• Inward displacement of the aortic wall calcification by more than 10mm (calcium sign).
• Cardiac enlargement (pericardial effusion).
• Left sided pleural effusion.
• Left apical opacity (apical cap).
• Tracheal displacement to the right.

Further reading https://emedicine.medscape.com/article/416776-overview#a2