An “evolving EKG” is often mentioned for a patient suffering from acute coronary syndrome (UA, NSTEMI, or STEMI). As the term implies, EKGs change over time in a patient with at-risk or actively infarcting tissue. You should monitor EKGs and be able to answer the following questions:
- does the patient have pain at the time the EKG was taken?
- did the patient improve with nitroglycerin or another intervention at the time the EKG was taken?
Knowing the answers to those questions will give you a clue about the severity and type of event the patient is having.
This is the typical progression of wave changes you can expect to see on the EKG:
- ST depressions
- “straightening” of ST segments
- ST elevations
- Q waves once the infarct is completed
- ST elevations in the setting of Q waves of old infarct are not as impressive as this could just be the tissue stretching over areas of old scar.
- A “stuttering course” of a STEMI may at times look like an NSTEMI, but it’s just the natural progression of the course. That’s because in a STEMI, you may see spontaneous reperfusion (plaque rupture) that causes the ST elevations to be hidden. But then you get additional vasospasm that may increase ST elevations.