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{{Short description|Elevation of the ST segment on an electrocardiogram}}
[[File:ST elevation illustration.jpg|thumb|Illustration of ST segment elevation]]
'''ST elevation''' is a finding on an [[electrocardiogram]] wherein the trace in the [[ST segment]] is abnormally high above the baseline.

==Electrophysiology==
The ST segment starts from the J point (termination of [[QRS complex]] and the beginning of ST segment) and ends with the [[T wave]]. The ST segment is the plateau phase, in which the majority of the myocardial cells had gone through [[depolarization]] but not [[repolarization]]. The ST segment is the [[isoelectric line|isoelectric]] line because there is no voltage difference across [[cardiac muscle]] cell membrane during this state. Any distortion in the shape, duration, or height of the [[cardiac action potential]] can distort the ST segment.<ref name="Erwin 2018">{{cite journal |last1=Erwin Christian |first1=de Bliek |title=ST elevation: Differential diagnosis and caveats. A comprehensive review to help distinguish ST elevation myocardial infarction from nonischemic etiologies of ST elevation |journal=Turkish Journal of Emergency Medicine |date=17 February 2018 |volume=18 |issue=1 |pages=1–10 |doi=10.1016/j.tjem.2018.01.008 |pmid=29942875|pmc=6009807 }}</ref>

==Abnormalities==
[[File:Pathologic ST elevation (CardioNetworks ECGpedia).png|right|thumb|upright=2|Examples of pathologic ST elevation. [[LVH]], [[LBBB]], [[Pericarditis]], [[Hyperkalemia]], Anterior [[Myocardial infarction|AMI]], [[Brugada syndrome]].]]
[[File:ConcaveDown.jpg|thumb|An example of mildly elevated ST segments in V1 to V3 that are concave down]]
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 0.1 [[millivolt|mV]] (usually representing 1 [[Millimetre|mm]] or 1 small square) in a limb lead or 0.2 mV (2 mm or 2 small squares) in a [[precordial lead]].<ref>[http://www.fpnotebook.com/cv/exam/StElvtn.htm Family Practice Notebook > ST Elevation] Retrieved November 2010</ref> The baseline is either the PR interval or the TP interval.<ref>{{cite book|last=Khandpur|first=R.S.|title=Handbook of biomedical instrumentation|year=2003|publisher=Tata McGraw-Hill|location=New Delhi|isbn=978-0-07-047355-3|page=255|url=https://books.google.com/books?id=C-rbT_c69oUC&pg=PA255|edition=2nd}}</ref> 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%.<ref>{{cite book |author=Sabatine MS|title=Pocket Medicine (이소연)|publisher=Lippincott Williams & Wilkins |year=2000 |isbn=978-0-7817-1649-9 }}{{page needed|date=December 2014}}</ref>

===Myocardial infarction===
[[File:12 Lead EKG ST Elevation tracing color coded.jpg|thumb|12-lead [[electrocardiogram]] showing ST-segment elevation (orange) in I, aVL and V1–V5 with reciprocal changes (blue) in the inferior leads, indicative of an anterior wall myocardial infarction.]]
When there is a blockage of the [[coronary artery]], there will be lack of oxygen supply to all three layers of [[cardiac muscle]] (transmural ischemia). The leads facing the injured cardiac muscle cells will record the action potential as ST elevation during [[systole]] while during [[diastole]], there will be depression of the PR segment and the PT segment. Since PR and PT interval are regarded as baseline, ST segment elevation is regarded as a sign of myocardial ischemia. The opposing leads (such as V3 and V4 versus posterior leads V7–V9) always show reciprocal ST segment changes (ST elevation in one lead is followed by ST depression in the opposing lead). This is highly specific for myocardial infarction. An upsloping, convex ST segment is highly predictive of a myocardial infarction ([[Harold E. B. Pardee|Pardee sign]]) while a concave ST elevation is less suggestive and can be found in other non-ischaemic causes.<ref name="Erwin 2018"/> Following infarction, [[ventricular aneurysm]] can develop, which leads to persistent ST elevation, loss of S wave, and T wave inversion.<ref name="Erwin 2018"/>

Weakening of the electrical activity of the cardiac muscles causes the decrease in height of the [[R wave]] in those leads facing it. In opposing leads, it manifests as [[QRS complex#Q|Q wave]]. However, Q waves may be found in healthy individuals at lead I, aVL, V5 and V6 due to left to right depolarisation.<ref name="Erwin 2018"/>

===Myocarditis/pericarditis===
In these conditions, there will mostly be concave ST elevations in almost all the leads except for aVR and V1. These two leads, ST depression will be seen because they are the opposing leads of the cardiac axis. PR segment depression is highly suggestive of pericarditis. R wave in most cases will be unaltered. In two weeks after pericarditis, there will be upward concave ST elevation, positive T wave, and PR depression. After several more weeks, PR and ST segments normalised with flattened T wave. At last, there will be T wave inversion which will take weeks or months to vanish.<ref name="Erwin 2018"/>

==Associated conditions==
The 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.{{cn|date=February 2021}}

It can be associated with:
* [[Myocardial infarction]] (see also [[Electrocardiography in myocardial infarction|ECG in myocardial infarction]]). ST elevation in select leads is more common with myocardial infarction. ST elevation only occurs in full thickness infarction
* [[Prinzmetal's angina]]<ref name="The only EKG book you will ever need">{{cite book|last=Thaler|first=Malcolm|title=The only EKG book you'll ever need|year=2009|publisher=Lippincott Williams & Wilkins|isbn=978-1-60547-140-2 |url=https://books.google.com/books?id=wQfzn-2UIaoC&q=the+only+ecg}}{{page needed|date=December 2014}}</ref>
* [[Acute pericarditis]]<ref name="pmid18052017">{{cite journal |vauthors=Tingle LE, Molina D, Calvert CW |title=Acute pericarditis |journal=American Family Physician |volume=76 |issue=10 |pages=1509–1514 |date=November 2007 |pmid=18052017 |url=http://www.aafp.org/link_out?pmid=18052017}}</ref><ref name="pmid16228101">{{cite journal |vauthors=Chew HC, Lim SH |title=Electrocardiographical case. ST elevation: is this an infarct? Pericarditis |journal=Singapore Medical Journal |volume=46 |issue=11 |pages=656–660 |date=November 2005 |pmid=16228101 |url=http://www.sma.org.sg/smj/4611/4611me2.pdf}}</ref> ST elevation in all leads (diffuse ST elevation) is more common with acute pericarditis.
* [[Left ventricular aneurysm]]<ref name="FroelicherMyers2006">{{cite book|author1=Victor F. Froelicher|author2=Jonathan Myers|title=Exercise and the heart|url=https://books.google.com/books?id=HXw-Tsr1c8AC&pg=PA138|access-date=10 October 2010|year=2006|publisher=Elsevier Health Sciences|isbn=978-1-4160-0311-3|pages=138–}}</ref>
* [[Blunt trauma]] to the chest resulting in a cardiac [[contusion]]<ref>{{cite journal |vauthors=Plautz CU, Perron AD, Brady WJ |title=Electrocardiographic ST-segment elevation in the trauma patient: acute myocardial infarction vs myocardial contusion |journal=The American Journal of Emergency Medicine |volume=23 |issue=4 |pages=510–516 |date=July 2005 |pmid=16032622 |doi=10.1016/j.ajem.2004.03.014}}</ref>
* [[Hyperkalemia]]<ref name="The only EKG book you will ever need"/>
* [[Acute myocarditis]]<ref name="The only EKG book you will ever need"/>
* [[Pulmonary embolism]]<ref name="The only EKG book you will ever need"/>
* [[Brugada syndrome]]<ref name="The only EKG book you will ever need"/>
* [[Hypothermia]]<ref name="The only EKG book you will ever need"/>
* [[J-point]] elevation<ref name="The only EKG book you will ever need"/>
* Early repolarization{{cn|date=February 2021}}
* Subarachnoid hemorrhage{{cn|date=February 2021}}

==See also==
* [[ST segment]]
* [[ST depression]]

== References ==

{{reflist|30em}}

{{Heart diseases}}

[[Category:Cardiac arrhythmia]]

ST elevation - Revision history

imported>WP Ludicer at 10:12, 12 August 2024