Abstract
Left atrial appendage aneurysm (LAAA) is a rare congenital anomaly, usually identified incidentally on a chest radiograph performed for another indication. Our case is that of an 11-month-old male infant who was incidentally diagnosed as having a giant LAAA while being clinically evaluated for pneumonia. The lesion was accurately diagnosed on preoperative, non-contrast, free-breathing cardiac MRI (CMR). LAAA has a peculiar appearance, resembling a "giant dog ear"-a sign first described on cardiac angiography and holding true on CMR as well. Fast free-breathing sequences on CMR, especially on 3 T, provide high-resolution images and eliminate the need for other pre-operative imaging that are either invasive, involve radiation exposure, require general anaesthesia or a combination of these.