October 25, 2015

A 2:1 AV block is not right away a Mobitz II

Most 12 lead ECG's are random captures of cardiac activity. For STEMI cases, the 12 lead will do but for arrhythmia recognition longer strips are needed.

Image 1 - covered 2:1 


Image 2 - covered 2:1 

Image 3 - 2:1 

The strips in images 1 and 2 are intentionally covered to simulate what you see in a 2:1 AV block. Image 3 is the 10 sec full disclosure strip. All manifest 2:1 AV conduction. Most would right away jump into the conclusion that this is second degree AV block type II (Mobitz II). Be refrained in labeling such strips as such until you see a longer strip.

Image 4 - Image 1 uncovered

Image 1 is a Mobitz I

Image 5 - Image 2 uncovered

Image 2 is also a Mobitz I

Image 6 - Image 3 transition strip

Image 3 is a Mobitz II

You might think that Image 2 which shows a right bundle branch block (RBBB)configuration is a Mobitz II but transition strips indicates this is Mobitz I. The RBBB in this case is fixed.

A 2:1 AV block is unique form or subtype of second degree AV block. This is not Mobitz II. A 2:1 AV block can either be due to Mobitz I or Mobitz II. YOU NEED A LONGER STRIP TO NAIL THE DIAGNOSIS.

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