EKG of the Week

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+ EKG Interpretation

Dr. Ohlbaum's Explanation

Sinus rhythm, 2nd degree AV block, Mobitz I (ie Wenkebach)

There are clear P waves marching through the EKG in a regular rhythm. They are normal looking P's so it is sinus rhythm. Some of those P's are conducted (for example the first 2) some are not (the 3rd for ex) so we know it is 2nd degree AV block where some P's conducted, some not. That makes the QRS's irregular (in contrast with 3rd degree where QRS's perfectly regular at junctional or ventricular rate).

So, is it Mobitz I or II? If you look with calipers at first and second PR or the ones in middle of EKG or at end of EKG you can see that PR is lengthening so it is Mobitz I. This tracing is interesting in that some areas are 2:1 conduction- that can be hard because if that is all you see for a whole tracing, one conducted P and next one not, you cannot TELL if it is Mobitz I or II but here we have the times when there are 2 conducted before the dropped one so you can look at the lengthening PR and call it Mobitz I.

Additional questions to ask yourself:

  • Anatomically, where is the block in this rhythm?
  • Is this something we should be concerned about - why does Mobtiz I not progress to third degree block and Mobitz II does?
  • What are the common etiologies?

For more information check out the article below

Further Reading:

Follow up EKGs:

Full EKG Index