Monday, August 17, 2009

NONSPECIFIC ST-T WAVE CHANGES

courtesy uptodate.com

NONSPECIFIC ST-T WAVE CHANGES — Nonspecific ST-T wave abnormalities are very common and may be seen in any limb or precordial lead of the electrocardiogram. The changes may be seen in all of the limb and precordial leads (diffuse changes), or they may be present only in the inferior, lateral, or anterior leads.

The types of abnormalities are varied and include straightening of the ST segment, ST segment depression or elevation, flattening of the T wave, or T wave inversion (show ECG 1). Causes of these changes include:

  • Electrolyte abnormalities
  • Post-cardiac surgical state
  • Anemia
  • Fever
  • Acidosis or alkalosis
  • Catecholamines
  • Drugs
  • Acute abdominal process
  • Endocrine abnormalities
  • Metabolic changes
  • Cerebrovascular accidents
  • Diseases such as myocarditis, pericarditis, cardiomyopathy, pulmonary emboli, infections, amyloidosis, systemic diseases, lung diseases

Abnormal T waves and ST segments may also be seen in healthy individuals, including well trained athletes.

ST-T WAVE CHANGES ASSOCIATED WITH SPECIFIC DISEASE STATES — Specific patterns of ST-T wave changes may be seen in association with various disease states.

Ischemia — ST-T wave abnormalities that are suggestive of subendocardial myocardial ischemia may be present diffusely in many leads; more commonly they are localized to the leads associated with the involved region of the myocardium (show ECG 2). (See "Electrocardiogram in the diagnosis of myocardial ischemia and infarction"). Typically there are ST segment changes associated with T wave flattening or inversion; isolated T wave changes are not usually seen with ischemia.

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