Abstract
A 31-year-old woman presented to the emergency department with atypical retrosternal chest pain and dyspnoea. Investigations initially revealed atrial flutter on her electrocardiogram and an interatrial septal mass on CT angiography of the chest. Additional workup with cardiac MRI and transoesophageal echocardiogram were able to delineate the cardiac mass. Electrophysiology and cardiothoracic surgery were consulted. The mass was excised in the same hospitalisation and the pathology report demonstrated a bronchogenic cyst. After mass excision, the patient chest pain has decreased, and she reverted back to normal sinus rhythm. On further follow-up, her flecainide and metoprolol were stopped.