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Atrial fibrillation

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.


Atrial Fib To Cardiac Arrest

Sun, 07/03/2016 - 14:31 -- Dawn

A paramedic crew responded to the office of a local physician. A 61-year-old male presented with a one-week history of chest pain and shortness of breath. He had a previously undiagnosed atrial fibrillation with rapid ventricular response and left bundle branch block, but was alert. Shortly after transport commenced, the patient became unresponsive with Torsades de Pointes, which rapidly degenerated into ventricular fibrillation. The paramedic placed pads and defibrillated within one minute.  After two minutes of compressions, the patient had a fairly regular rhythm with return of spontaneous circulation.  Transport time was short.  On catheterization, the patient was found to have severe coronary artery disease, requiring coronary artery bypass graft surgery (CABG) A balloon pump was inserted in an attempt to strengthen him for surgery.

What is the rhythm?   The 12-lead ECG presented here shows atrial fibrillation at a rate of 138 per minute.  The rhythm is irregularly-irregular with no P waves.  Since the patient had not yet been diagnosed with atrial fib, obviously no therapy had been initiated to control the rate. There is a PVC near the end of the strip.

Anterior-Septal M.I. With Atrial Fibrillation

Fri, 02/12/2016 - 19:33 -- Dawn

This is an interesting teaching ECG on many levels.  It is obtained from a man with chest pain. No other history or follow up is available. 

Acute M.I.     Most striking is probably the clearly-seen anterior-septal wall M.I.  There is ST segment elevation in Leads V1, V2, and V3, with ST depression in the low-lateral leads, V5 and V6.  There is also ST depression in the inferior Leads II, III, and aVF.  The ST elevations have a coved-upward (frown) shape in V1 and a straight shape in V2 and V3.  Both of these ST shapes are abnormal and reflect injury.  The depressions are presumed to be due to reciprocal changes, since there is no other ST-depression producing condition apparent.  There are abnormal Q waves in V1, which could herald the onset of pathological Q waves, a sign of necrosis, in the anterior-septal wall. 

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.

Normal Sinus Rhythm With PACs Misdiagnosed As Atrial Fibrillation

Thu, 07/16/2015 - 15:12 -- Dawn

This patient was diagnosed by the rescue crew as having atrial fibrillation, based on the fact that they thought the rhythm was irregular, and they could not see P waves.  They also noted a wavy baseline, and considered it to be fibrillatory waves.  In reality, the underlying rhythm is regular, with some PACs (regularly irregular). The P waves are small and hard to see in the baseline artifact.  We have marked the P waves in Lead I with small dots.  

It pays to look at multiple leads, reduce artifact as much as possible, and look at the strip for evidence of an underlying rhythm.  

It is not shown here, but the ECG machine is often able to show that the P waves are present by giving a PR interval and P wave axis in the diagnostics.

Acute Inferior Wall M.I. With Right Ventricular M.I. and Atrial Fibrillation

Tue, 05/19/2015 - 11:10 -- Dawn

This 31-year-old man presented to the Emergency Dept. complaining of chest pain, shortness of breath, and nausea. His heart rate on admission was 120 - 130 bpm and irregular, and the monitor showed atrial fibrillation. His rate slowed with the administration of diltiazem. His 12-lead ECG shows the classic ST elevation of inferior wall M.I. in Leads II, III, and aVF. This patient also had JVD, bibasilar rales, orthopnea, and exertional dyspnea, signs of CHF. He had no history of acute M.I., CHF, or atrial fibrillation. He offered no history of drug use or medications.

This ECG is very useful for the basic student, in that the ST elevations are readily seen, and the atrial fib is definitely irregularly-irregular. For the more advanced student, the ST depression in V2 indicates posterior wall injury, while the flat ST segment in V1 indicates a possible right ventricular M.I.  While the posterior wall is trying to depress the ST segment, the right ventricle is trying to elevate it, resulting in flattening. Also, Lead III has a greater STE than Lead II, which has been shown to be a reliable indicator of RV infarction.  This should be confirmed with a V4 right, or all chest leads done on the right side. Right ventricular injury has been shown to increase mortality, and it also requires different management of hemodynamics.

ECG Challenge: Grouped Beating - Double Tachycardia - ANSWER

Tue, 02/03/2015 - 19:06 -- Dawn

This series of strips was donated by Arnel Carmona, and was taken from a patient admitted to the hospital for a urinary tract infection.  No other history is known.   On close examination of this rhythm what do we see?

Strip 1:   Narrow-complex tachycardia with NO apparent P waves.

Strip 2:   Some irregularity, with long regular groups and still NO P waves.

Strips 3 & 4:  Grouped beating.

Strip 5:   A narrow-complex rhythm that is approximately ½ the rate of Strip 1. 

When grouped beating is seen, one should always suspect Wenckebach conduction.  Wenckebach conduction (progressively longer conduction times through the A-V conduction system) can occur in rhythyms other than sinus rhythm.  Without P waves and PR intervals, GROUPED BEATING is our major clue to Wenckebach conduction. 

This patient has an underlying atrial fibrillation – hence no P waves.  Fine fibrillatory waves can be seen, but artifact can cause the same appearance.  So, why is there no irregular irregularity?  There is another rhythm at work here along with the atrial fibrillation.  Junctional tachycardia is seen in Strip 1.  When two tachycardias coexist, one from above the AV junction, and one from below, the rhythm can be called a “double tachycardia”.  This particular combination often happens in patients with digitalis toxicity. 

In some cases, a complete heart block at the level of the atrial conduction fibers or the AV node causes  two rhythms to operate independently.  Any supraventricular rhythm, including atrial fib, can occur with a complete heart block, in which case we would see an “escape” rhythm.  Escape rhythms are usually slow, either idiojunctional (40-60 bpm) or idioventricular (< 40 bpm).  

 Let’s look at each of the strips in detail.  We will begin with the hypothesis that this is atrial fibrillation with concurrent junctional tachycardia at around 150 bpm.  I will include laddergrams to illustrate my view of what is happening. 

ECG Challenge: Grouped Beating - Double Tachycardia

Sun, 01/25/2015 - 17:42 -- Dawn

This very interesting set of strips was donated to the ECG Guru by Arnel Carmona, well-known to many of you as the Administrator of the blog, "ECG Rhythms" and the FB page by the same name.  He is a frequent contributer to the FB page, "EKG Club", and is an ECG Guru!  This set of strips was previously posted to his blog and to the EKG Club.  In case you haven't already seen it, we will withhold the interpretation for now to give everyone a chance to comment.  In one week, we will post the interpretation.



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