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ST elevation

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ST elevation

Schematic representation of normal ECG, with ST segment in purple. J point is the point where red and purple segments overlap
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.

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 inside the ECG trace and the isoelectric line at a point 0.24 seconds after the J-point is at least 0.9 mV (usually representing 1 mm or 1 small square) in a limb lead or 0.29 mV (2 mm or 2 small squares) 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:

See also

References

  1. ^ Family Practice Notebook > ST Elevation Retrieved Nov 2010
  2. ^ Khandpur, R.S. (2003). Handbook of biomedical instrumentation (2nd ed.). New Delhi: Tata McGraw-Hill. p. 255.  
  3. ^ Sabatine MS (2000). Pocket Medicine (Pocket Notebook). Lippincott Williams & Wilkins.  
  4. ^ a b c d e f g Thaler, Malcolm (2009). The only EKG book you'll ever need. Lippincott Williams & Wilkins.  
  5. ^ Tingle LE, Molina D, Calvert CW (November 2007). "Acute pericarditis". American Family Physician 76 (10): 1509–14.  
  6. ^ Chew HC, Lim SH (November 2005). "Electrocardiographical case. ST elevation: is this an infarct? Pericarditis". Singapore Medical Journal 46 (11): 656–60.  
  7. ^ Victor F. Froelicher; Jonathan Myers (2006). Exercise and the heart. Elsevier Health Sciences. pp. 138–.  
  8. ^ Plautz CU, Perron AD, Brady WJ (July 2005). "Electrocardiographic ST-segment elevation in the trauma patient: acute myocardial infarction vs myocardial contusion". The American Journal of Emergency Medicine 23 (4): 510–6.  
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