This image is beloved of cardiac radiologists. The heart is displaced to the left so much that the right heart border fails to project beyond the spinal shadow. The left heart border is lumpy with a prominent main pulmonary artery segment. This sounds like an ASD, but the clue here is the step in the left heart outline between the aortic knuckle and the pulmonary artery. This is because there is no pericardium between the two to smooth the outline; indeed there is complete absence of the left pericardium. Nothing else looks like it . It is a benign pathology. Be careful not to call this a partial defect of the left pericardium, in which there is no cardiac shift, and although there may well be a strange looking bulge on the upper left heart border, it looks nothing like this. Partial defect is a life threatening condition.