Video review: Atrial fibrillation (A-fib) on the ECG. Tips for students and new nurses!
Here are 3 things to notice in this rhythm review looking at rapid atrial fibrillation:
The rhythm is irregular. Not only that, but it’s IRREGULARLY irregular. This means we have no way to guess where the next QRS complex will land.
The QRS complex is narrow, <0.12 seconds, suggesting an origin that’s above the ventricles. This leaves us with sinus, atrial, or junctional possibilities.
There are no discrete P waves. At first glance, these small humps may be tricky but take a closer look. Those are actually the T waves. One thing we can do to help with this is examine the relation to the QRS complex and when we do, we see that this gives us a consistent QT interval which is helpful.
Contrast this with:
In sinus tachycardia with premature atrial complexes (PACs) by comparison, we’d expect a regular underlying rhythm with isolated early beats. Regular indicates that the rhythm marches out with an expected cadence.
In junctional rhythms, we also expect the ventricular response pattern to march out, since the impulses are coming from a reliable pacemaker source in the heart (the AV node or junction).
And finally, in Second degree Type I heart blocks (Mobitz I, Wenckebach) we expect to see a progressive lengthening of the PR interval preceding dropped QRS complexes. In this type of conduction defect, the irregular ventricular response is a result of P waves that are failing to elicit a ventricular depolarization.
I hope this helps, and keep in mind everything here is presented from a single lead basic rhythms perspective. Exceptions may exist in the real world!
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