STsegmentele

STsegmentele refers to the ST segment(s) of the electrocardiogram (ECG or EKG), the flat interval between the end of the QRS complex and the beginning of the T wave. The ST segment typically lies on the baseline and represents the early phase of ventricular repolarization. In most leads the segment is isoelectric, though small deviations can occur due to position, conduction, or lead placement.

Clinical relevance and interpretation

STsegmentele changes are used to diagnose acute and chronic cardiac conditions. Pathologic ST elevations or depressions are assessed in relation to the baseline, in contiguous leads that reflect the same anatomical region. ST elevation can indicate acute myocardial injury, such as a ST-elevation myocardial infarction (STEMI), or conditions like pericarditis or early repolarization patterns. ST depression can suggest myocardial ischemia or subendocardial infarction. Other factors, including electrolyte disturbances, medications, or normal variant patterns, can influence the ST segment. Diffuse ST elevations with concurrent PR depression are characteristic of pericarditis, while widespread, concave ST elevations with a notch at the J point may reflect early repolarization.

Measurement and considerations

Assessment of the ST segment involves comparing its level to a defined baseline, often the TP segment or a stable isoelectric line. Contiguity of leads matters: changes are more clinically meaningful when seen in several neighboring leads corresponding to the same territory of the heart. It is important to consider patient factors such as age, heart rate, and electrode placement, which can affect the appearance of the ST segment.