ECG tutorial: ST and T wave changes


ST and T wave changes may represent cardiac pathology or be a normal variant. Interpretation of the findings, therefore, depends on the clinical context and presence of similar findings on prior ECGs.


Nonspecific ST-T wave changes are very common and may be seen in any lead of the electrocardiogram. The changes may be seen in all or most of the leads (diffuse changes), or they may be present contiguous leads, such as the inferior, lateral, or anterior leads.

The types of abnormalities are varied and include subtle straightening of the ST segment, actual ST segment depression or elevation, flattening of the T wave, biphasic T waves, or T wave inversion (waveform 1). In the absence of a clinical history or symptoms, T wave abnormalities and flattened and depressed ST segment changes are nonspecific. Causes of these changes include:

  • Functional and physiologic variants (eg, post-prandial)
  • Electrolyte abnormalities
  • Post-cardiac surgical state
  • Anemia
  • Fever
  • Acidosis or alkalosis
  • Endogenous catecholamines
  • Drugs, such as digoxin
  • Acute abdominal process
  • Endocrine abnormalities
  • Metabolic changes
  • pH changes
  • Cerebrovascular accidents
  • Diseases such as myocarditis, pericarditis, cardiomyopathy, pulmonary emboli, infections, amyloidosis, systemic diseases, lung diseases
  • Myocardial ischemia

Flat T waves and small ST segment changes may also be seen in healthy individuals, including well trained athletes, leading to mistaken diagnosis of heart disease. T wave inversions, however, are more concerning for cardiomyopathy or other cardiac syndrome, depending on the clinical context.


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Literature review current through: Mar 2014. | This topic last updated: Jan 3, 2013.
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