Electrocardiogram (ECG) findings showing ST-segment depression in a wide range of leads and STsegment elevation in aVR are found in patients with acute coronary syndrome with multivessel coronary lesions and left main trunk lesions. A 64-year-old man with a history of eosinophilic granulomatosis presented with chest pain and dyspnea. Although an ECG showed the above findings, he was diagnosed with acute severe aortic regurgitation (AR) complicating aortic root dissection and successfully underwent urgent Bentall operation. These ECG findings indicated that acute severe AR caused subendocardial ischemia.