Because unstable ischemic syndromes have rapidly changing supply versus demand characteristics, a single ECG may not accurately represent the entire picture.

In spite of these limitations, the 12 lead ECG stands at the center of risk stratification for the patient with suspected acute myocardial infarction.

Mistakes in interpretation are relatively common, and the failure to identify high risk features has a negative effect on the quality of patient care.

[10] Based on symptoms and electrocardiographic findings, practitioners can differentiate between unstable angina, NSTEMI and STEMI, normally in the emergency room setting.

[11] Other calculators such as the GRACE[12] and HEART [13] scores, assess other major cardiac events using electrocardiogram findings, both predicting mortality rates for 6 months and 6 weeks, respectively.

[citation needed] Sometimes the earliest presentation of acute myocardial infarction is the hyperacute T wave, which is treated the same as ST segment elevation.