ST elevation
ST elevations refers to a finding on an electrocardiogram, wherein the trace in the ST segment is abnormally high above the isoelectric line.
Measurement
An ST elevation is considered significant if the vertical distance between the ECG trace and the isoelectric line at a point 0.04 seconds after the J-point is at least 0.1 mV (usually representing 1 mm) in a limb lead or 0.2 mV (2 mm) in a precordial lead.[1] The isoelectric line is either the PR interval or the TP interval.[2] 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%.[3]
Physiology
The ST segment corresponds to a period of ventricle systolic depolarization, when the cardiac muscle is contracted. Subsequent relaxation occurs during the diastolic repolarization phase. The normal course of ST segment reflects a certain sequence of muscular layers undergoing repolarization and certain timing of this activity. When the cardiac muscle is damaged or undergoes a pathological process (e.g. inflammation), its contractile and electrical properties change. Usually, this leads to early repolarization, or premature ending of the systole.
Associated conditions
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.
It can be associated with:
- Myocardial infarction (see also ECG in myocardial infarction). ST elevation in select leads is more common with MI.
- Prinzmetal's angina[4]
- Acute pericarditis.[5][6] ST elevation in all leads is more common with acute pericarditis.
- Left ventricular aneurysm[7]
- Blunt trauma to the chest resulting in a cardiac contusion[8]
- Hyperkalemia[4]
- Acute myocarditis[4]
- Pulmonary embolism[4]
- Brugada syndrome[4]
- Hypothermia[4]
- J point elevation[4]
See also
References
- ^ Family Practice Notebook > ST Elevation Retrieved Nov 2010
- ^ Khandpur, R.S. (2003). Handbook of biomedical instrumentation (2nd ed.). New Delhi: Tata McGraw-Hill. p. 255. ISBN 9780070473553.
- ^ Sabatine MS (2000). Pocket Medicine (Pocket Notebook). Lippincott Williams & Wilkins. ISBN 0-7817-1649-7.
- ^ a b c d e f g Thaler, Malcolm (2009). The only EKG book you will ever need. Lippincott Williams & Wilkins. p. 2009. ISBN 1605471402, 9781605471402.
{{cite book}}: Check|isbn=value: invalid character (help) - ^ Tingle LE, Molina D, Calvert CW (2007). "Acute pericarditis". Am Fam Physician. 76 (10): 1509–14. PMID 18052017.
{{cite journal}}: Unknown parameter|month=ignored (help)CS1 maint: multiple names: authors list (link) - ^ Chew HC, Lim SH (2005). "Electrocardiographical case. ST elevation: is this an infarct? Pericarditis" (PDF). Singapore Med J. 46 (11): 656–60. PMID 16228101.
{{cite journal}}: Unknown parameter|month=ignored (help) - ^ Victor F. Froelicher; Jonathan Myers (2006). Exercise and the heart. Elsevier Health Sciences. pp. 138–. ISBN 9781416003113. Retrieved 10 October 2010.
- ^ http://www.ncbi.nlm.nih.gov/pubmed/16032622
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