DESCRIPTION

An irregular rhythm with no P waves preceding the QRS complexes essentially defines atrial fibrillation. If the ventricular response to the atrial fibrillation is slow enough, you can see the irregular, squiggly (highly technical scientific description) baseline between the QRS complexes, which comes from the fibrillating atria. If the QRS complexes are abnormally wide (from a bundle branch block) you will have to use a certain amount of that commodity called “good judgment” to decide if what you are seeing is in fact atrial fibrillation with a bundle branch block, or ventricular tachycardia; the irregularity of the rhythm and a squiggly baseline in between QRS complexes will argue in favor of atrial fibrillation.

HABITAT

Anywhere at all, but more commonly in the elderly and the hypertensive. This rhythm used to be found in the Rheumatic Heart Disease Clinic, but that habitat has vanished (at least in developed countries) and its inhabitants have become almost extinct.

CALL

“The heart rate’s 150 again!”

RESEMBLANCE TO OTHER ARRHYTHMIAS

Anything that’s irregular can make you think atrial fibrillation; be sure you look carefully for P waves in front of QRS complexes where there’s enough space to see them if they’re actually there. Computers seem to have particular trouble with irregular rhythms, frequently calling sinus rhythm with premature atrial complexes (PACs) atrial fibrillation. That’s a good thing for us, since it means clinical cardiologists still have a job overreading computerized ECG interpretations, at least for the time being. Just make sure there aren’t P waves that are small and hard to see before you brazenly call out “atrial fibrillation!” and look silly.

CARE AND FEEDING

The first thing to do is slow down the ventricular response, and anything that blocks the atrioventricular (AV) node is likely to work. Diltiazem, verapamil, β-blockers, digoxin, alone or in combination will usually do the trick. Remember that oral drugs take some time to get absorbed and work, while intravenous boluses work quickly but will wear off just as quickly unless repeated or followed by an intravenous infusion of the drug. How slow should we aim for? Dr. Goldilocks, that famous electrophysiologist, always would say, “Not too fast, not too slow, just right!” You get the idea. Maybe a rate of around 60–80 would be acceptable to her although recent data suggest less aggressive heart rate control may work as well.1 Another thing to think (argue) about is what sort of anticoagulant would be most appropriate to reduce the patient’s risk of stroke. There are two documents that will help you answer this and any other question you might think of about atrial fibrillation.2 Finally, should you try to convert it? The Spanish Inquisition aside, if the arrhythmia is super-rapid and hemodynamically unstable, a biphasic jolt of a few hundred joules will work wonders. Otherwise, it can still be a topic of some controversy, so I’d take those documents I just mentioned and go sit somewhere for the four hours it will take you to get through them, and if you’re lucky, the rhythm will have converted spontaneously to sinus if it was of recent onset (up to 50% will!) leaving you looking like a genius.

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