What is typically absent in an EKG of a patient with unstable angina?

In a patient with unstable angina, the characteristic finding on an EKG is the absence of significant ST segment elevation. Unstable angina is categorized as a form of acute coronary syndrome where there is a temporary reduction in blood flow to the heart muscle without resulting in myocardial injury, which means that the heart muscle has not undergone necrosis.

In contrast, ST segment elevation typically indicates myocardial infarction (heart attack), where there is a significant injury to the heart muscle due to prolonged ischemia. Since unstable angina does not lead to necrosis, the EKG will not exhibit the significant ST segment elevation that one would expect in a full-blown myocardial infarction.

T wave inversions can be present in cases of unstable angina and indicate certain types of ischemia, but they do not define its absence as a hallmark feature. The QRS complexes may demonstrate some changes, but these are not definitive indicators for distinguishing unstable angina. Heart rate abnormalities can occur but are not a defining characteristic of unstable angina. Thus, the lack of significant ST segment elevation is a critical distinction in the EKG interpretation for unstable angina.