Strip 67

atrial flutter


First Glance:

From across the room it looks like atrial flutter with a variable block.

Discussion:

This strip has a lot of squiggles. We see big fat QRS complexes in both leads, over a classic ‘sawtooth’ baseline. Sawtooth implies that the baseline is choppy, regular, and does not have a flat baseline with intermittent waves like we might see in a sinus or atrial tachycardia. If we count small boxes, it looks like the sawtooth is running around 320 bpm or so, which is an expected rate for atrial flutter. The upper lead looks like it has positive P waves with a fairly flat baseline, but the lower lead’s baseline is so regular and classic-appearing for flutter that I’m sticking to my guns.

Atrial flutter usually has a neatly synchronized QRS that follows or overlaps a flutter (‘F’) wave the same way everytime the QRS fires. Here we see that this relationship is not always held up. If you look in the lower lead, sometimes the flutter wave seems to be in the middle of a wave when the QRS fires, and sometimes it is at the end. This could be because the flutter baseline is actually artifact, or it could actually be atrial fibrillation and there is no regular relationship. It could also be because there is some unpredictability in the AV node and perhaps a second degree AV block is causing a varied AV delay and the resulting various F-QRS intervals. My electrophysiology mentors take this one step further, noting that the AV node can actually have multiple levels of blocking, and this can cause even more irregular conduction despite a regular supraventricular source.

The T waves are negative in the upper lead, and positive in the lower lead. This is not useful to us because that could be normal or abnormal depending on which lead these are, and that bit got ripped off.

Final Impression?

Atrial flutter with variable block (3:1 to 6:1), ventricular rate of ~95 bpm, suspicious for AV node disease.

Management implications:

Check lead placement, and evaluate with 12L for ischemia as necessary.

 

The rate is unlikely to cause hemodynamic compromise, although in the very sick heart the loss of coordinated atrial kick could significantly reduce the cardiac output. Atrial flutter responds better to cardioversion than afib.

 The Take-home Point:

A classic sawtooth baseline strongly pushes you in the atrial flutter direction, but it is not infallible. This could also be a fast atrial ectopic tachycardia, or artifact, or the most likely of the differentials: atrial fibrillation.

You can have a strip that looks like flutter but is actually atrial fibrillation for a couple reasons. First, you can have a flutter baseline that is not perfectly regular. This is atrial fibrillation. A great example is here and its explanation is near the bottom of the page by the picture here.

This can happen because you have have one atrium in flutter (thereby seeing regular flutter waves in certain leads) while the other atrium is in fibrillation. Whenever you have both concurrently, you call it atrial fibrillation. You could also have atrial fibrillation but one chunk of the atrial myocardium has a large reentry loop giving certain leads a regular or almost regular flutter appearance. This is analogous to the separate atria fib/flutter possibility just mentioned. And as before, it is still called afib, and will act electrically as such.

 

 

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