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A Fib

ECG Basics: Onset of Atrial Fibrillation

Fri, 12/16/2016 - 19:44 -- Dawn

This strip shows the onset of atrial fibrillation.  A fib can be "paroxysmal," meaning that it has a sudden onset, but then stops spontaneously, usually within 24 hours to a week.  A fib can also be classified as "persistent", meaninging that the a fib lasts more than a week.  It can stop spontaneously, or be halted with medical treatment.  "Permanent" a fib is a fib that is resistent to treatment.  

The first three beats in this strip represent sinus rhythm at 75 beats per minute.  At the onset of atrial fibrillation with beat number four, the rhythm becomes irregularly irregular, and the rate is around 140-150 bpm. We can expect new-onset a fib to have a fast ventricular rate, as the atria are sending hundreds of impulses to the AV node every minute. The AV node will conduct as many of those impulses as it can to the ventricles.  Most AV nodes can easily transmit 130-160 bpm.  In a fib, the atria are quivering, not contracting. Because of this fibrillation of the atrial muscle, a fib has no P waves, and therefore, no "atrial kick".  The contribution of the atria to cardiac output (25-30%) is lost. An extremely fast rate can also lower output and overwork the heart, so one treatment goal for a fib is to lower the rate.  This can be done independently of attempts to convert the rhythm.

During a fib, blood clots can form in parts of the atria, especially the left atrial appendage.  If sinus rhythm is restored after these thrombi form, they can embolize and travel to the brain, causing stroke.  Before electively converting atrial fib to a sinus rhythm, the patient may need to be anticoagulated.

 

ECG Basics: Atrial Fibrillation With A Rapid Ventricular Response

Fri, 12/18/2015 - 23:11 -- Dawn

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.

ECG Basics: Atrial Fibrillation With a Rapid Ventricular Response

Sun, 07/26/2015 - 13:54 -- Dawn

This rhythm strip is recorded in two simultaneous leads, which is always preferable to one single lead.  It is a good example of atrial fibrillation with a rapid ventricular response.  Atrial fib that has not been treated will usually have a rapid ventricular rate.  This reflects the ability of the AV node to conduct a tachycardia, within limits.  The natural slow conduction of the AV node allows it to act as a "filter", preventing the huge numbers of impulses generated by the atrial fibrillation from reaching the ventricles.  In this case, about 140 beats per minute are able to make it through the AV node into the ventricles.   In some patients, preexisting cardiac conditions such as valve insufficiency or CHF may make this rate dangerous for the patient.  The rate may lower cardiac output in some people, and this must be considered in light of the fact that the loss of P waves in atrial fib also lowers cardiac output significantly.

ECG Basics: Atrial Fibrillation With Rapid Ventricular Response

Thu, 03/13/2014 - 10:54 -- Dawn

This is a good rhythm strip to use to illustrate how atrial fibrillation can almost look regular when the rate is fast.  Students should be taught how to "march out" the rhythm for regularity.  It is always a good idea with atrial fib to take a longer strip, looking for the inevitable "gaps" in the R-to-R intervals.  Also, as your students progress, a 12-lead ECG is invaluable to really search for P waves.  Even two or three simultaneous leads are better than just one.

ECG Basics: Atrial Fibrillation With A Controlled Ventricular Response

Mon, 11/25/2013 - 01:07 -- Dawn

Atrial fibrillation with a controlled ventricular response is often considered to be atrial fib that has been controlled with medication.  While this is often true, it is possible to see atrial fib with a ventricular rate between 50 and 100 bpm in a patient who has not been treated.  The hallmark signs of atrial fib are:  no P waves and irregularly-irregular rhythm.

Multiple, simultaneous leads are advised to be sure there are no P waves, and a long rhythm strip is often needed to prove the irregularly-irregular rhythm.  Remember, even though this rate is adequate (about 90 bpm), the loss of P waves means no "atrial kick".  The atria are not filling the ventricles with a forceful pumping action. Patients can lose a significant percentage - up to 25% - of their cardiac output because of this.  Coupled with the risk of stroke from the formation and embolization of blood clots from the sluggish circulation in the atria, it is much preferable to have sinus rhythm at the same rate.

ECG Challenge From Dr. Ahmed - Patient With Hyperkalemia

Fri, 07/26/2013 - 16:03 -- Dawn

This ECG was kindly donated to the ECG Guru website by Dr. Ahmed for open discussion among our members.  The patient was a 70+ year-old man who presented with a complaint of dizziness.  His serum potassium level was found to be 6.5 (normal is 3.5 - 5.0).  Upon correction of his K levels, his rhythm was atrial fibrillation at 130 / min.

WHAT DO YOU THINK ABOUT THIS INITIAL ECG?  What is causing the slow rate? Is there atrial activity?  Do you see QRS morphology changes?  What about the anterior ST and T wave changes? 

We look forward to hearing from our members!  And thanks to Dr. Ahmed for donating this interesting ECG.

 

ECG Basics: Atrial Fibrillation With A Rapid Ventricular Response

Wed, 06/05/2013 - 22:46 -- Dawn

This is a good basic rhythm strip example of atrial fibrillation with a rapid ventricular response showing the identifying characteristics of atrial fibrillation:  no P waves, an irregularly-irregular rhythm, and a "fibrillatory" baseline.  The wavy baseline will not be seen in all leads in all patients, so it is best to use the first two findings as diagnostic criteria.  Atrial fib often appears initially as a rapid rhythm, as the AV node is being bombarded by many impulses from multiple foci (pacemakers) in the atria.  Depending upon the AV node's ability to transmit these impulses,however, we could see a slow, normal, or rapid ventricular response. 

Atrial fib has very chaotic depolarization of the atrial muscle, resulting in quivering and ineffective pumping of the atria.  This loss of "atrial kick" can severely reduce ventricular filling, and can reduce cardiac output by as much as 25%.  In patients with a very rapid rate, cardiac output can be further reduced, causing CHF.  In addition, the fibrillating atria can form blood clots due to sluggish movement of blood.  These clots can embolize and cause stroke.  For these reasons, patients with atrial fib are anticoagulated and sometimes the atrial fib is stopped by medical, surgical, or electrical therapy.  Recurrence of atrial fib is common after treatment, and for some patients, control of the ventricular rate and anticoagulation become the preferred treatment.

Anterior Wall M.I. With Atrial Fibrillation

Tue, 09/04/2012 - 13:59 -- Dawn

A good teaching ECG, showing clearly elevated ST segments in V1 through V4.  This patient had an LAD occlusion.  In addition, he has new-onset atrial fib at a rate of about 120/min.  Atrial fib has decreased cardiac output because of the loss of P waves prior to the QRS complexes, and a resultant decreased ventricular filling pressure.  In addition, this fast rate contributes to increased myocardial oxygen demand and damage.  An early priority, along with getting this patient to PCI, is slowing the rate.

Atrial Fibrillation With A Rapid Ventricular Response

Wed, 05/16/2012 - 15:52 -- Dawn

This is a good example of atrial fibrillation with a rapid ventricular response. The rate is around 150 per minute, and the rhythm is almost regular.  Show your students how to "march out" the QRS complexes so they can see the irregularity.  When the rate is around 150, also check for atrial flutter with 2:1 conduction.  In this case, none of the 12 leads shows strong evidence of flutter waves, but it is a possibility when the rhythm is almost regular.  Fortunately, the initial treatment for both AFib and AFlutter with rapid response are the same.

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