Isolated right ventricular infarction (RVI) is a rare event. The electrocardiographic (ECG) pattern of RVI, ST-elevation in lead V4R and in anterior chest leads V1-3 is similar to that of a proximal occlusion of a small, nondominant right coronary artery (RCA). The ECG changes may be misinterpreted as signs of infarction of the anterior wall. This paper describes a case of isolated temporary occlusion of the major side branches of the RCA during percutaneous coronary intervention, recognized by angiography findings and typical ECG changes. This case demonstrates how one might avoid wrong decisions even in the catheterization laboratory by putting attention to the anatomical interpretation of the ECG.