68-year-old woman with paroxysmal atrial fibrillation

We present the case of a 68-year-old woman, currently asymptomatic but with a history of paroxysmal atrial fibrillation and tachycardia-bradycardia syndrome, for which she underwent a DDD pacemaker implantation and was started on oral anticoagulants. A recent chest X-ray (figure 1), for respiratory infection, was performed and the patient was referred to our institution for evaluation. Following diagnostic procedures, the patient was successfully operated on. heartjnl;105/8/656/F1F1F1Figure 1Preoperative chest X-ray (A) and chest CT with contrast (B). QUESTION: What is the most likely diagnosis?Mitral stenosis.Pericardial cyst.Left atrial appendage aneurysm.Left atrial myxoma.Atrial septal defect.