sinus rhythm with a PVC
First Glance:
From across the room it looks like sinus with some ectopy.
Discussion:
A straightforward strip for the first 9 beats. We can see positive then negative biphasic P waves before every QRS in the lower trace, consistent with a septal lead. The voltage calibration is unknown. The PR interval is markedly long, at around 260 ms. The QRS is borderline with around a 120 ms width, but not knowing which leads this is we would be guessing randomly about conduction delays- all we can say if there might be something. There is T inversion in the upper lead, and what looks like a smidge of ST elevation in the lower lead which is impossible to evaluate given the unknowns about calibration.
It looks like there is a PVC two beats from the right, then a pause. Closer inspection reveals even more unusual activity.
Close inspection of beat 9 shows that the P wave is different. The PR interval is similar, but now the P has almost disappeared in the lower trace, and appeared in the upper trace. Close inspection of the RR interval shows that beat 9 comes around 80ms earlier than expected. Beat 9 is probably a PAC. Beat 10 could be a PVC, or it could be a fusion beat with another atrial beat, or it could be another PAC but with aberrancy. We don’t see any convincing atrial activity before beat 11, so this could be a junctional escape beat, or maybe we just aren’t picking up on subtle atrial activity.
Final Impression?
Normal sinus rhythm with unknown aberrancy and first degree block @ 60 bpm, with some ectopy.
Management implications:
Check leads, get 12L, and so on. The PVC is nonspecific, as noted in the last strip.
The Take-home Point:
First degree block is a PR interval > 200ms. It is caused by delay in the AV node or the His bundle before the bundle branch split.
It can be unremarkable in a resting athlete with high vagal tone, or consistent with mild conduction disease in a patient without that clinical correlation. A borderline wide QRS could also potentially indicate conduction disease.
With a PR interval as long as the one in this strip, you can feel confident there is disease of the AV node. Disease of the His bundle would not cause delays this long, but would be likely to just block instead.
One star strip. Students should identify the rhythm correctly.