[Angina-induced marked, positive U-waves in leads V1-3].

U-wave changes during angina are often not recognized, although a change in U-wave polarity may be the only sign of myocardial ischemia. The appearance of a positive U-wave in leads V1-4 during angina suggests posterobasal ischemia and critical stenosis of the CX or RCA coronary artery. The authors present two examples.