Schematic representation of normal ECG, with ST segment difference between stable and unstable angina pdf purple. ST elevations refers to a finding on an electrocardiogram wherein the trace in the ST segment is abnormally high above the baseline.
An ST elevation is considered significant if the vertical distance inside the ECG trace and the baseline at a point 0. 04 seconds after the J-point is at least 0. The baseline is either the PR interval or the TP interval. The ST segment corresponds to a period of ventricular contraction.
Because of the complete depolarization of the ventricles, represented by the QRS complex, in theory there is no net movement of charge during the ST segment. In the case of depolarization, healthier cells will typically displace a larger amplitude and duration of depolarization. During systole, a ventricle with subepicardial ischemia will exhibit cells with higher amplitude of depolarization in the cardiac endocardium.
This vector points away from the chest EKG leads, causing a downward deflection in the TP segment. However, since the TP segment is the baseline of the EKG, the machine corrects for this by raising TP to baseline which results in ST elevation. Repolarization of the ventricle normally occurs during the T wave, however one cause of ST segment elevation is the early repolarization of the heart wall. This is referred to as .
The exact topology and distribution of the affected areas depend on the underlying condition. Thus, ST elevation may be present on all or some leads of ECG. ST elevation in select leads is more common with MI. Acute pericarditis ST elevation in all leads is more common with acute pericarditis.