The current subject matter relates to indicating extent and location of myocardial ischemia in a patient. Electrodes can be placed on a body of the patient. Signal amplifiers can receive orthogonal electrical signals from the electrodes via three bipolar leads. The signal amplifiers can amplify the signals and send the amplified signals to analog to digital converters. The analog to digital converters can convert the amplified signals to digital signals. A computing device can execute a data analysis application that can receive these digital signals, generate QRS complexes associated with these signals, generate depolarization vectors associated with these QRS complexes, and then determine changes in magnitudes and directions of these vectors. Based on the changes in magnitudes and directions, the data analysis application can determine and display extent and location of myocardial ischemia in the patient. Related apparatus, systems, methods, techniques and articles are also described.