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ST segment


The normal ST is isoelectric. Elevation or depression is judged in relation to the PR segment.

Some changes may be normal:

  • Limb lead depression or elevation up to 1mm and in left precordial leads of up to 2mm.
  • J‐depression: the J point (junction between the QRS and ST segment) is depressed without sustained ST depression i.e. depression with a gentle upward slope.
  • Early repolarisation in adolescents: the ST segment is elevated and concave in leads with an upright T wave.

Others are pathological, either:

  • a downward slope of the ST followed by a biphasic inverted T or
  • a sustained horizontal ST segment depression 0.08 sec or longer

ST segment

Pathological ST segment changes are commonly associated with T wave changes and occur in:

  • Pericarditis
  • Myocardial ischaemia or infarction
  • Severe ventricular hypertrophy (ventricular strain pattern)
  • Digitalis effect

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