September 16, 2016

Mobitz I with wrong lead placement

A 70 y.o complaining of chest pain. What is the ECG interpretation?

Image 1 - ECG case

Image 2 - ECG case marked

This is an irregular rhythm with group-beating (black oval) with a non-conducted P wave (marked blue asterisk). In lead II, the P waves are inverted and there are Q waves. So, is this junctional rhythm with delayed atrial conduction vs. ectopic atrial rhythm with second degree AV block type I (Mobitz I) or AV Wenckebach with 3:2 and 2:1 AV conduction?

The P waves are inverted in lead II. Does it "really" mean that these are junctional beats with delayed atrial conduction or ectopic atrial rhythm?

There are also Q waves. Does it "really" mean that this patient had an old myocardial infarction?
To answer those questions, we need the full disclosure strip.

Image 3 - Full disclosure strip

Image 3 showed inverted P waves and QRS in lead I and upright P and QRS in aVR. There must WRONG LEAD PLACEMENT in this case. So, I asked the nurse to correct lead placement.

Image 4 - Full disclosure after lead placement correction

The nurse said, the leads are "all over the place". Image 4 is after lead placement correction. It showed upright P and QRS in lead I as well as in lead II. The P wave is also inverted in aVR.
Learning Point/s for those used to 2 leads:

It is high time to "move-on" or transition from reading 2 leads (lead II and V1) and read telemetry tracings in "FULL DISCLOSURE". By looking at all leads, you will be accustomed or used to the configuration of QRS complexes and detect wrong lead placement and not make wrong interpretations (In this case an old myocardial infarction because of a Q wave in lead II and a junctional rhythm vs ectopic atrial rhythm because of an inverted P wave in lead II).

Final Interpretation:
Sinus rhythm, second degree AV block type I (Mobitz I) or AV Wenckebach with wrong lead placement.



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