Rhythm Challenge #1

What’s the heart rhythm?

*** Update 12/28/09 ***

Hint: These are certainly atrial complexes (blue arrows) but are they P-waves?


  • Billy says:

    I believe it's multifocal atrial tachycardia. I was trying to talk myself into some sort of block due to the extra P waves, but I think that the varying P wave morphology (and varying T wave morphology because of buried P waves), varying PRI in spots, and varying R-R in some spots makes MAT a better choice.A 12 lead would be nice to look at here (especially V1).

  • Scott says:

    Long time lurker, first time replyer:I'm seeing wide QRS complexes and thinking it's an intermittent complete AV block.

  • Christopher says:

    I too would love a 12L.I've got three guesses:- Wenckebach (2AV Mobitz I) conduction w/ a variable drop rate. This screen is small, but I swear the PRi elongates before dropping.- AV dissociation, atrial rate ~200, accelerated junctional rhythm. If I'm not seeing elongation, maybe I'm seeing dissociation.- WAP w/ blocked conduction through the AV node for those hanging P waves.Regardless, I'm thinking there is some pathology creating this that I should seek out. Rate appears appropriate, so I'm thinking the pt is probably hemodynamically stable. Rx should probably be "treat the patient not the monitor" 🙂

  • Tom B says:

    @Billy – Sorry, bud! No 12-lead ECG for this one! @Scott – Thanks for reading my blog! I'm glad you left a comment. I agree the complexes look a bit wide, but it's difficult to say whether or not they are 120 ms. I'm not sure it's a complete AV block, but I do think there's variable AV conduction! @C.Watford – I've spoiled you guys with 12-leads! I'd like to see if anyone revises their guess based on the graphic I provided.I'll give you another hint. The patient was taking an antiarrhythmic that slowed down his atrial rate.Tom

  • akroeze says:

    I'll be totally wild based on your hint here and guess that this is some kind of atrial flutter.I'll admit that I would never call it that based on this strip without other info added.

  • Tom B says:

    Ding! Ding! Ding! You get the cigar, Alex. This is a case of atrial flutter with variable AV conduction and an unusually slow flutter rate. Good job!Tom

  • Christopher says:

    Bah, the unusual rate for the waves made me completely leave out a-flutter. Maybe some better PRi scrutiny, as it appears shortened in some. Good strip!

  • Shaggy says:

    Damn. I was thinking this was flutter until I read the comments, especially by C. Watford, so I felt humiliated and waited to see how it turned out. You have to admit, Watford is usually bang right on!

  • Tom B says:

    Oh, yes. He is surprisingly strong with the force for a first-year paramedic! :)Tom

  • Anonymous says:

    Definitely a-Flutter! Definitely not WAP: IF they were p waves, there were not 3 or more varying morphologies. I watch about 50 rhythms a day all day as a monitor technician…this stuff's groovy! glad you have a spot on the net for this, thanks!

  • Tom B says:

    Anonymous – You're welcome! I recorded this many years ago when I watched 32 rhythms all day as a monitor technician! :)Tom

  • Hillis says:

    Well i was thinking about atrial flutter from the begining- the ECG shows in some part the classical tooth like apperance of the P wave which favor the diagnosis , but was quite confused from the answers of my collegues that's why i prefered to wait !!!! May i ask what is WAP reffered to ?? Very interesting challenge and ready for the next one ..Many thanks

  • Tom B says:

    You're welcome, Dr. Hillis! Since this was well received, perhaps I will do a new rhythm challenge each month.Tom

  • Mark P says:

    Atrial tachycardia with variable AV block – classic presentation of digoxin toxicity. Was he on digoxin Tom?
    If it was CHB you would expect the escape rhythm to be regular; the pauses suggest AV conduction.

  • john says:

    atrial flutter with varaiable conduction and bundle branch block

  • phillip says:

    I was leaning to aflutter with variable block, too fast and not regular for Heart Blocks any medication history

  • Tom B. says:

    Mark P. –

    I regret that I don’t remember any details about the patient. This was recorded on the Critical Care Stepdown unit back in 1997.


  • Emeline says:

    I’ll try to put this to good use immidetaely.

  • Mike C says:

    MCL-1 can be very useful in this situation

  • arnel says:

    This is atrial tachycardia with variable conduction

  • Troy says:

    I believe the underlying atrial rhythm is a multi-foci firing (I.e. wandering atrial pacemaker) with a Mobitz type II block. The PRi is variable but consistent with an WAP rhythm but the dropped beats are due to the very sick AV node. Looks very similar to a COPD pt I had who had a prox LAD occlusion. Good strip!!

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