Look Closely (this is not AF)

A pt with h/o CAD, CABG, CHF, DM, CRI is c/o SOB.

#whatistherhythm?

Image 1

At first glance you will say it is AF but looking closely IT IS NOT AF.

If you measure the R to R from R1 to R 8, the RR interval is the same. There is slight prolongation in between R8R9 vs the preceding RR. R9R10 interval is less than 2x the RR of the preceding RR interval.

If it is regular then this could not be AF unless there is an existing AF with junctional rhythm with entrance and exit block. There is however a distinct P wave before R10.Using a caliper, you can march our distinct P waves (if you sharpen your eyes). The PRI in R9 is longer than in R10. PRI in R11 is longer  than R10. So, there is a Wenckebach (long stretch or atypical Wenckebach). Sometimes, we just have to sharpen our eyes and try to isolate artifacts from  the true waves.

Image 2

At one point, this type of Wenckebach is read as first degree AV block (image  2)

Here is the clearer view of the Wenckebach cycle.

Image 3

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