ST Elevation on ECG: Understanding the Electrophysiological Process

Electrophysiological Basis of ST Elevation

The American College of Cardiology states that ST elevation on an ECG represents an injury current flowing across the boundary between ischemic and non-ischemic zones of the myocardium, indicating abnormal ventricular repolarization that can signify acute myocardial injury 1, 2
ST elevation occurs during the plateau phase of the ventricular action potential, which corresponds to early repolarization of the ventricles 2
The ST segment normally begins at the J point and represents the period when the ventricles have been completely depolarized 1
During normal cardiac function, the ST segment should be isoelectric 3

The American Heart Association, as published in Circulation, notes that ST elevation is caused by an "injury current" that flows between damaged and healthy myocardium 4
In acute myocardial infarction, the injury current is due to the flow of electrical current across the boundary between ischemic and non-ischemic zones 2
This current creates a vector that points toward the area of injury, causing ST elevation in leads facing the injured area 4

The European Society of Cardiology recommends that ST elevation ≥0.1 mV in at least two contiguous leads is a key diagnostic criterion for STEMI 7
The American College of Cardiology suggests that the threshold for abnormal J-point elevation varies by lead, gender, and age, with specific values for men and women 1
Continuous ST-segment monitoring can identify transient ischemia and has prognostic value for predicting complications and mortality, as noted in Circulation 8

ST elevation in leads V1-V4 typically indicates anterior wall ischemia/infarction involving the left ventricle, caused by occlusion of the left anterior descending coronary artery, according to Circulation 4
ST elevation in leads II, III, and aVF indicates inferior wall infarction, typically involving the right coronary artery or left circumflex coronary artery, as published in Circulation 4

The shape of ST elevation has prognostic significance, with certain patterns associated with increased likelihood of severe left ventricular dysfunction, as noted in Circulation 5
ST elevation with a horizontal or downsloping pattern is more specific for myocardial ischemia than upsloping ST elevation, according to Circulation 5