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10. ST Segment Abnormalities

Topics for study:

  1. General Introduction to ST-T and U Wave Abnormalities
  2. ST Segment Elevation
  3. ST Segment Depression


General Introduction to ST, T, and U wave abnormalities

Basic Concept: the specificity of ST-T and U wave abnormalities is provided more by the clinical circumstances in which the ECG changes are found than by the particular changes themselves. Thus the term, nonspecific ST-T wave abnormalities, is frequently used when the clinical data are not available to correlate with the ECG findings. This does not mean that the ECG changes are unimportant! It is the responsibility of the clinician providing care for the patient to ascertain the importance of the ECG findings.

Factors affecting the ST-T and U wave configuration include:

"Secondary" ST-T Wave changes (these are normal ST-T wave changes solely due to alterations in the sequence of ventricular activation):

"Primary" ST-T Wave Abnormalities (ST-T wave changes that are independent of changes in ventricular activation and that may be the result of global or segmental pathologic processes that affect ventricular repolarization):

Differential Diagnosis of ST Segment Elevation

Normal Variant "Early Repolarization" (usually concave upwards, ending with symmetrical, large, upright T waves)

Example #1: "Early Repolarization": note high take off of the ST segment in leads V4-6; the ST elevation in V2-3 is generally seen in most normal ECG's; the ST elevation in V2-6 is concave upwards, another characteristic of this normal variant.

image 12-05

Ischemic Heart Disease (usually convex upwards, or straightened)

Acute Pericarditis

Other Causes:

Differential Diagnosis of ST Segment Depression

Normal variants or artifacts: