This report describes the presentation and evaluation of an elderly man with uncorrected tetralogy of Fallot. The patient had remained fairly asymptomatic for much of his life. He presented to the hospital at age 86 with new-onset atrial fibrillation with rapid ventricular response and a non-ST-segment elevation myocardial infarction. Transthoracic and transesophageal echocardiography revealed infundibular pulmonic stenosis with a ventricular septal defect, overriding aorta, and right ventricular hypertrophy, findings consistent with unrepaired tetralogy of Fallot. Severe right ventricular pressure overload was also present. Coronary angiography revealed nonobstructive coronary artery disease. It was felt that the rapid atrial fibrillation resulted in right ventricular subendocardial ischemia that improved following restoration of sinus rhythm. After a systematic literature search, the authors believe this case represents the oldest reported patient with the diagnosis of uncorrected tetralogy of Fallot and serves as an example of a well-balanced congenital shunt.