What is the significance of the st segment

March 12, Article Information. Berry, MD; Perry G. An, MD; David M. Dudzinski, MD, JD. Access through your institution. Add or change institution.

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Measure content performance. Develop and improve products. List of Partners vendors. It is one type of myocardial infarction in which a part of the heart muscle myocardium has died due to the obstruction of blood supply to the area. The ST segment refers to the flat section of an electrocardiogram ECG , in particular, the flat section that connects two distinct complexes on the tracing the QRS complex and the T wave. When a person has the most severe type of heart attack, this segment will no longer be flat but will appear abnormally elevated.

ACS occurs when a plaque ruptures from within a coronary artery, causing the partial or complete obstruction of that artery.

The obstruction itself is caused when blood clots form around the area of the rupture. When obstructed, the portion of the heart muscle serviced by that artery will quickly suffer from a lack of oxygen, called ischemia. Chest pains angina are often the first signs of this. If the obstruction is extensive enough, some of the heart muscle will begin to die, resulting in myocardial infarction. ACS is categorized by the level of obstruction and the resulting damage to the heart muscle:.

Regardless of how an ACS event is classified, it is still considered a medical emergency since unstable angina and NSTEMI are often early warning signs of a major heart attack. Ventricular pacing with a pacing wire in the right ventricle causes ST segment abnormalities identical to that seen in LBBB. There is appropriate discordance , with the ST segment and T wave directed opposite to the main vector of the QRS complex.

Widespread ST elevation with concave pericarditis-like morphology in a patient with severe traumatic brain injury. ST depression due to subendocardial ischaemia may be present in a variable number of leads and with variable morphology. Widespread ST depression with ST elevation in aVR is seen in left main coronary artery occlusion and severe triple vessel disease.

ST depression localised to the inferior or high lateral leads is more likely to represent reciprocal change than subendocardial ischaemia. The corresponding ST elevation may be subtle and difficult to see, but should be sought. This concept is discussed further here. There is ST elevation in the posterior leads V Supraventricular tachycardia e. This rate-related ST depression does not necessarily indicate the presence of myocardial ischaemia, provided that it resolves with treatment.

Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. I do not believe that is correct. This site uses Akismet to reduce spam. Learn how your comment data is processed. EKG Library. Ed Burns. Robert Buttner. One comment Hello!