A 65-year-old woman presented with a history of dyspnea and atypical chest pain. She was diagnosed with a non-ST-segment elevation myocardial infarction due to a giant right coronary artery aneurysm. After a failed percutaneous embolization, she was scheduled for right coronary artery aneurysm resection, posterior descending artery revascularization and mitral valve repair. During the induction of anesthesia and institution of mechanical ventilation, the patient suffered cardiovascular collapse. The transesophageal echocardiographic examination revealed tamponade physiology owing to compression of the cardiac chambers by the unruptured aneurysm, which resolved with the sternotomy. The surgery was carried out uneventfully.