Strip 20

not atrial fibrillation


First Glance:

From across the room it looks like afib with a PVC.

Discussion:

I was really going to put this in the growing afib pile, but it’s not that simple. This strip is clearly irregular, but there are two sections of reasonable regular beats with subtle but present P waves. See here:

Marked above in magenta are fine baseline changes consistent with atrial activity. It would be easy to write this off as a fibrillatory baseline, but the fact that they are seemingly consistent from beat to beat suggest otherwise. The PR interval is on the long side, but not quite a first degree block in this lead.

At the end of this little excerpt is a similar QRS, but with slightly different axis and slightly wider. This beat (green triangle) is early, and is either a fusion beat or a premature supraventricular beat where the conduction pathway had not completely repolarized yet.

Beats 4-8 are similar. Then there is a PVC at beat 10. The groups of seemingly sinus-paced beats are not mechanically perfectly at a certain rate, but seem more consistent with a sinus arrhythmia (beat to beat variation of >160ms) with some slow beats and some faster groups.

Final Impression?

Likely marked sinus arrhythmia @ ~90 bpm, plus one PVC and a fusion vs aberrant supraventricular beat.

Management implications:

Sinus arrhythmia is adaptive, and tells us the patient has a functioning autonomic system. If there is any doubt (and there is doubt here) examining other leads for better atrial views will be necessary. If the standard leads don’t show us the light, a Lewis lead might crack this case. The marked changes between beat-to-beat rates might suggest there is more pathology than just a sinus arrhythmia, however, and some suspicion for a diseased sinus node should be maintained.

 The Take-home Point:

Afib is not the only irregularly irregular rhythm.

Many supraventricular rhythms can look just like afib on the monitor, including marked sinus arrythmia, all manner of sinus and AV blocks (especially if they are transient or irregular), atrial flutter with variable block, wandering pacemaker and multifocal atrial tachycardia, sick sinus syndrome, and probably a dozen more.

 

 

2purple_starTwo star strip. The meat and potatoes.

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