ST elevation: differentiation between ST elevation myocardial infarction and nonischemic ST elevation.

It is well accepted that early reperfusion is beneficial in patients with acute myocardial infarction presenting with ST elevation (STE). Earlier studies suggested lack of beneficial effects in patients presenting without STE and even with ST depression. Currently, time to reperfusion is considered to be a quality of care measure, and the latest American College of Cardiology/American Heart Association guidelines for the treatment of STE acute myocardial infarction (STEMI) emphasize that the physician at the emergency department should make reperfusion decisions within 10 minutes of performing the initial electrocardiogram (ECG). However, not all ECGs with STE necessarily reflect transmural infarction from acute thrombotic occlusion of an epicardial coronary artery, as a large number of patients presenting with compatible symptoms have baseline STE. In some cases a pattern of benign nonischemic STE (NISTE) can be recognized fairly easily. Other times, differentiating between true STEMI and NISTE may be difficult. It should be remembered that patients presenting with chest pain and showing benign pattern of NISTE (eg, "early repolarization" or STE secondary to left ventricular hypertrophy) may have true ischemic pain and non-STE myocardial infarction or even STEMI on top of the baseline benign pattern. It seems that, in the "real world," the ability of physicians to differentiate NISTE from STEMI based on the presenting ECG pattern widely varies and depends on the prevalence of baseline NISTE in the patient population. Further studies are needed to assess the ability of various ECG criteria to accurately differentiate between STEMI and NISTE.