 The intracoronary electrocardiography i.c. ECG is a very sensitive method for ischemia detection. The i.c. ECG reacts earlier on ischemia; the changes are much more prominent and easy to register. The wire tip could be positioned directly in different regions and thus to map regional ischemia. In most of the studies and from our own observations became evident that when surface ECG do not react the i.c. ECG demonstrates significant changes in ST-segment and QRS complex. Moreover, the registration of i.c. ECG is very cheap and needs only an adapter connecting coronary wire end and ECG. An i.c. ECG also can differentiate residual ischemic changes in distal main vessel and side branch as sources of prolonged ischemia, respectively - source of periprocedural myonecrosis. 