A 62 year old female presents to the ED complaining of chest pain. Vital signs are within normal limits.
Her EKG is below.
1. What does the EKG demonstrate?
2. What do these findings represent?
Q waves in leads II, III, aVF, V3-V6
An old infero-lateral MI
The EKG shows a sinus rhythm with Q waves in leads II, III, aVF, V3-V6. This represents an “old” or “completed” inferolateral MI.
There is no way to tell from the EKG when the MI happened. It may have been 2 days ago or 20 years ago. The only way to get an idea is to compare this EKG to a prior EKG. If the prior EKG from 2 months ago was normal and today’s EKG shows an old inferolateral MI, then we know the patient had an MI at some time during the last 2 months. To try to pin down when it happened, we would need to correlate it with when the patient had symptoms and the results of cardiac enzymes.
Q waves are sometimes a normal part of a QRS complex. To differentiate normal Q waves from pathological Q waves (meaning representing an old MI), we have to look at the width and the depth of the Q wave. Normal Q waves should be narrow and shallow. Pathological Q waves are wide and deep. If the Q wave is 1 small box wide and the depth of the Q wave is >25% of the size of the entire QRS complex, that is abnormal and that Q wave likely represents an old MI. For example, on this EKG, in lead III, the Q wave is 2 boxes wide. The depth of the Q wave is approximately 6 mm while the entire QRS complex is approximately 8 mm. 6/8 is much more than 25% so we know this Q wave is pathological and represents an old MI.