The Many Faces of Ischemia

The ECG ST segment and T waves take on a variety of changes in the setting of inadequate blood supply, or ischemia (see illustration). ST segment elevation is the most time sensitive and important change to recognize. Patients with ST segment elevation require transport to hospitals capable of percutaneous coronary intervention (PCI). That said, there are other ECG changes that occur in the setting of injury. Transport patients with concerning or non  diagnostic ECGs to the closest appropriate facility.

Unfortunately, ischemia does not always "follow the rules." Non-specific ST-T segment changes and even "normal" ST-T segment morphology can be seen in the setting of unstable angina. Simply stated, the absence of typical ST segment changes like elevation or depression cannot rule out an active myocardial infarction. Pay special attention to a patient's history. Other concerning ST or T segment changes can include:

1) Hyperacute T waves (broad based and tall)
2) Non-specific T waves (flattened)

3) Normal ST-T segment