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.