EKG of the Week 9-4

An 83 y/o male with a history of “heart problems” presents to the ED after a fall. His EKG is below.

1.       What is the rhythm?

2.       What other abnormality does this EKG demonstrate?



The rhythm is atrial fibrillation.

The other abnormality is Q waves in leads II, III and aVF consistent with an old inferior wall MI.

The EKG demonstrates an irregular rhythm with absent P waves and an undulating baseline. This is consistent with atrial fibrillation.

The EKG also demonstrates Q waves in leads II, III and AVF. Q waves signify an old (or “completed”) MI.

Q waves can sometimes be normal.  How can we differentiate between normal Q waves and pathological Q waves which suggest an old MI?

For Q waves to be considered pathological, they should be at least one box wide. In addition, the height of the Q wave should be at least 25% of the height of the entire QRS complex. On this EKG, the Q wave in lead II is 3 mm and the entire QRS complex is 7 mm. In lead II, the Q wave is 9 mm to a QRS complex of 12 mm. In lead aVF, the Q wave is 6 mm to a QRS height of 9 mm.

Q waves suggest an old MI. However, there is no way to tell when that MI occurred. The only way to know is to compare this EKG to a previous EKG and to correlate it with the timing of the patient’s symptoms. If a previous EKG from four months ago was normal and today’s EKG shows Q waves, that suggests the patient had an MI at some point in the last four months.