Several tricks of a PJC in one strip

A pt s/p post surgery. Asymptomatic at this time.

Image 1 (rhythm strip lead 2)

It shows sinus rhythm with inverted waves before  R2 and after R10, a longer PRI in R5 and R8 and  AV dissociation in R12 and R14.

Image 2 Ladder diagram

All those findings is due to one phenomenon: premature junctional complex (PJC) affecting the behavior of the surface ECG. R2 with an inverted P wave and a PRI of about 0.16 sec due to a conducted PJC with a delayed anterograde conduction. That is why the PRI normal. 

R5 and R8 had a longer PRI compared to the rest because of concealed conduction of PJC's in the AV node. Concealed means not seen on the surface ECG but manifest as unexpected ECG behavior. In this case the sudden PRI prolongation. The "unseen" PJC made the partially refractory so that the next beat that is conducted in the AV node is delayed. This delay created the long PRI on the surface ECG.

The inverted P wave after R10 is due atrial depolarization of a PJC that is blocked going to the ventricles.

R12 and R14 are conducted PJC's but the atrium is depolarized by an impulse from the sinoatrial node. So, we see an upright P wave that is very close to a QRS which resulted to AV dissociation.



  1. Sorry, but I am skeptical … I fear there is just too much baseline artifact on this tracing, and too much variability in P wave morphology in lead II for beats that are being supposed as sinus for me to feel comfortable ruling out the possibility of PACs (which are actually much more common than PJCs as a cause of negative lead II P waves that conduct). Perhaps if there were additional tracings on this patient of better quality (and more consistent P wave morphology) — as well as other tracings that prove this patient is having PJCs — then perhaps there might be support for the diagnosis given …

    1. Here is another strip from same pt. -

  2. Thanks Arnel for providing another strip from the same patient (which you now do at — ). This additional tracing is a fascinating rhythm, for which I completely agree with your laddergram interpretation. But the point that I think ( = my opinion) is most important to emphasize — is that there is NO WAY one can make the diagnosis you made here WITHOUT also seeing clear evidence that: i) there is regular sinus activity (ie, consistent P-P interval with P wave morphology ALL the same); and ii) that this patient is having frequent PJCs (in this case junctional bigeminy). Once you know this (ie, by reviewing the additional tracing you now tell us there is on this patient) — THEN you can presume that a similar phenomenon is occurring here (as you did) — but that is NOT the information that you initially gave us … — :)