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10. ST Segment AbnormalitiesTopics for study:
General Introduction to ST, T, and U wave abnormalitiesBasic 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 ElevationNormal 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.
Ischemic Heart Disease (usually convex upwards, or straightened)
Acute Pericarditis
Other Causes:
Differential Diagnosis of ST Segment DepressionNormal variants or artifacts:
What does ST T abnormalities mean?ST-T abnormalities may represent preclinical cardiac involvement of CVRs more sensitively than LVH on ECG and ECG findings may be used in mass examinations.
What does ST and T wave abnormality mean?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 electrocardiograms. NONSPECIFIC ST-T-WAVE CHANGES.
Should I worry about T wave abnormality?Abnormalities of the T wave are associated with a broad differential diagnosis and can be associated with life-threatening disease or provide clues to an otherwise obscure illness.
What is anterior ischemia on an ECG?The anterior wall ischaemia/infarction involving the left anterior descending artery (LAD) is usually represented on the ECG with ST-T changes in the precordial leads and in leads I and aVL while those of the inferior wall classically involve leads II, III and aVF.
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