ST segment
Feature of an electrocardiogram
In electrocardiography, the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms).
It starts at the J point (junction between the QRS complex and ST segment) and ends at the beginning of the T wave. However, since it is usually difficult to determine exactly where the ST segment ends and the T wave begins, the relationship between the ST segment and T wave should be examined together. The typical ST segment duration is usually around 0.08 sec (80 ms). It should be essentially level with the PR and TP segments.
The ST segment represents the isoelectric period when the ventricles are in between depolarization and repolarization.
01Interpretation
- The normal ST segment has a slight upward concavity.
- Flat, downsloping, or depressed ST segments may indicate coronary ischemia.
- ST elevation may indicate transmural myocardial infarction. An elevation of >1mm and longer than 80 milliseconds following the J-point. This measure has a false positive rate of 15-20% (which is slightly higher in women than men) and a false negative rate of 20-30%.
- ST depression may be associated with subendocardial myocardial infarction, hypokalemia, or digitalis toxicity.
02In fetal monitoring
In fetal electrocardiography, ST waveform analysis (sometimes abbreviated STAN) is used to get an indication of increasing levels of fetal base deficit.
Sources and credits
This article is adapted from the Wikipedia article “ST segment”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- SinusRhythmLabels.svg by Created by Agateller (Anthony Atkielski), converted to svg by atom., Public domain
- ST segment elevation and depression.jpg by PeaBrainC, CC BY-SA 4.0
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