Saturday, September 27, 2014

A Mystery Rhythm, Explained by K. Wang's Ladder Diagram.

This was presented at the SMACC-Gold EKG workshop:
Can you figure it out?
See the answer below.

Here is a nice ladder diagram and explanation from K. Wang:

--The primary problem is irregular sinus bradycardia (sinus node dysfunction), with junctional escape beats (R1, 2, 3, 5, 6, 7,and 9, which occur with exactly the same interval) and two capture (conducted) beats (R4 and 8). 
--The patient also must have some degree of AV conduction problem both anterograde and retrograde. Otherwise, R2, 3, 6, and 7 would have resulted in retrograde P waves, or P2 and 5 would have conducted. 
--P3 and 6 occur with slightly longer RP interval than P2 or 5, which is the reason why they are conducted but still with a long PR interval.
--P1, 4, and 7 are completely assumed even though it is unusual for them to occur exactly within the QRS (too much of coincidence). Otherwise, P3P5 interval is too long not to have a P wave in between when P2P3 or P5P6 can occur.


  1. Couldn't P3 and P6 be premature atrial beats? I know the P waves all looks very similar, but those two do occur earlier. On the other hand the P3P4 and P4P5 intervals are the same.

    1. They could be, but would have to be located very close to the sinus node in order to have the same morphology.

  2. Very nice. Do You think Valsalva could help ?

  3. I think one alternate explanation would be that P-waves #1, #4, and #7 are actually further back into the T-wave than marked by Dr. Wang (the nadir). If we go to the first visible T-waves in V1 and V2, it appears that they have deformations consistent with atrial activity. Given each of the junctional complexes feature identical q-waves in II, and the P-amplitude is fairly large, I don't know that I would put them buried in the QRS. If we instead place them at the nadir of the T-wave on those beats, the P-P intervals would then decrease in duration until the jump...I'll email my proposed laddergram.

    This would lend itself towards a more exotic explanation of sinus bradycardia (~54 bpm), Type I SA Block (causing an effective slowing of the sinus rate to the mid-40s), a junctional escape rhythm (~50 bpm), and occasional capture beats.


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