Dawn's picture

This ECG rhythm strip has all the hallmarks of atrial fibrillation:  the rhythm is irregularly irregular and there are no P waves.  The rate is about 150 beats per minute. There is no P wave because the atria are being irregularly depolarized by many ectopic pacemakers at once, causing the atria to "quiver".  This patient has new-onset atrial fib, and has been medicated with a calcium channel blocker.  The rate shows signs of slowing, but has not reached the target rate for this patient of less than 80 bpm.

At the onset of atrial fib, the rate is usually fast, because the AV node is being bombarded by numerous impulses from the atria.  The impulses arrive irregularly, and with different "strengths".  The AV node conducts as many impulses as it is able to, usually resulting in a rate over 110-120 bpm.  Medications can affect the rate, of course, and we use medications to slow AV conduction and allow a more normal heart rate.  

There are many methods of correcting atrial fib, not always with permanent success. Some patients tolerate this rhythm well as long as the rate is kept in check.  But others suffer a loss of cardiac output due to the loss of "atrial kick", which is the forceful filling of the ventricles by the contracting atria.  This loss of cardiac output can severely impair some people, making it necessary to try to convert the atrial fibrillation.  In addition, people living with atrial fib must be anticoagulated, as the loss of forceful emptying of the atria can cause collections of blood clots which can break free and embolize.

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Jerry W. Jones MD FACEP's picture


Whenever I teach an advanced ECG class and the time arrives to discuss atrial fibrillation, I always ask this question: "What characteristic best defines atrial fibrillation?"

The answer is almost invariably "an irreguarly irregular rhythm!" And thus the fly enters the spider's web, because that is NOT the correct answer. The correct answer is "No P waves."

Why not "irregularly irregular rhythm?"

First, atrial fibrillation is NOT the only dysrhythmia that is irregularly irregular. Multifocal atrial tachycardia is irregularly irregular, atrial flutter with a variable AV block can be irregualrly irregular, a parasystolic focus with frequent ectopic beats can present with an irregularly irregular rhythm as well as a number of other rhythm and conduction disturbances.

Second, one may have atrial fibrillation with a perfectly regular rhythm. This was not at all unusual back in the days when digoxin was used more frequently for rate control in atrial fibrillation. With a slight digtoxicity, a high grade or even 3rd degree AV block would develop with a junctional or ventricular escape pacemaker - which would provide a precisely regular rhythm resulting in atrial fibrillation with a regular rhythm!

Try posing the same question (if you don't already) at your next conference and see what responses you get. But try to get the audience to specify just ONE main characteristic.


Jerry W. Jones, MD FACEP FAAEM


Twitter: @jwjmd

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