EKG of the Week 2018-2-4

A 62 year old female presents to the ED complaining of chest pain. Vital signs are within normal limits.

Her EKG is below.

2018 2-4.jpg

1.       What does the EKG demonstrate?

2.       What do these findings represent?

 

ANSWER:

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.