n coronary artery disease, transient ST elevation in precordial leads generally indicates anteroseptal ischemia. However, there are some cases where occlusion of a side branch during percutaneous transluminal coronary angioplasty (PTCA) of the proximal right coronary artery has induced right ventricular infarction and precordial ST elevation. [1][2][3][4] Right ventricular infarction usually accompanies inferior wall infarction, and rarely occurs alone, with such cases accounting for only about 3% of all cases of infarction. [1][2][3][4] We present a patient with transient isolated right ventricular branch ischemia occurring during PTCA of the right coronary artery and with marked ST elevation in the contralateral precordial leads. Case ReportIn April 2000, the patient, a 64 year-old man, experienced cold sweats and chest pain, lasting approximately 20-30 min, while eating dinner. He believed he was having a hypoglycemic attack and took some glucose tablets. Because of severe malaise, the patient visited a neighborhood doctor the following day where electrocardiographic abnormalities were identified and consequently he was admitted to hospital that same day. He had previously been diagnosed with a Japanese Circulation Journal Vol. 65, February 2001 stomach ulcer in 1968 and diabetes in 1980. He had smoked 20 cigarettes a day for 40 years, and his father is a diabetic.The patient was 163 cm tall and weighed 67 kg. His blood pressure was 124/56 mmHg, and his pulse rate was 56 beats/min, regular and did not have a left -right difference. There were no abnormalities in his heart sounds, respiratory sounds or abdomen.The results of clinical tests on admission showed elevated white blood cell count (14,020/ l), aspartate aminotransferase (74 IU/L), and creatine kinase (883 IU/L). Chest Xray revealed a cardiothoracic ratio of 43.8%, and there were no abnormal findings in the lung fields. Electrocardiography (Fig 1)