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Teaching Series: Atrial Fibrillation With Left Bundle Branch Block

Submitted by Dawn on Thu, 05/29/2014 - 23:28

This is a good example of atrial fibrillation with left bundle branch block.  You get two ECGs with this one, because the patient presented to EMS with a fast heart rate, and the rate was slowed with the drug diltiazem.  We do not have any other patient information, unfortunately.

In the first strip, we see a wide-complex tachycardia.  In an emergency situation, with an unstable patient, this rhythm could safely be treated using an emergency ventricular tachycardia (VT) protocol.  In fact, all WCTs should be considered to be VT until proven otherwise.  In most emergency settings, the unstable VT patient would be electrically cardioverted, which will often convert atrial fibrillation as well.  The stable patient with this rhythm would be treated with an antiarrhythmic drug, such as amiodarone.  This may convert or slow down atrial fib.  So, in the initial stages of treatment, differentiating between VT and A Fib is not the first priority.  Assessing the patient's hemodynamic stability and addressing the rate if necessary are the priorities.  

So, how do we know this is NOT VT?  It can be difficult, but in this case, the rhythm, even though fast, is very irregular.   VT is not always perfectly regular, but this irregularly-irregular rhythm points to atrial fibrillation. Also, the pattern of the QRS morphology fits with LBBB.  The criteria for LBBB are:  1) supraventricular rhythm, 2) wide QRS, 3) negative QRS in V1 with positive QRS in Leads I and V6.  If we assume the rhythm is atrial fibrillation, we meet the first criteria.  The other two are self-evident.

After the medication is administered, 10 minutes later, we see the rate slow down.  There is no change in the irregularly-irregular rhythm, and the LBBB pattern remains.  All that has changed is the rate and, hopefully, the patient's symptoms.  This confirms that the original rhythm was not VT.  

Remember, atrial fib lowers cardiac output because there is no P wave - no "atrial kick".  Also, the fast rate associated with new-onset atrial fib often compromises ventricular filling and cardiac output.   LBBB also has a deleterious effect on cardiac output.  Wide QRS complexes indicate that the ventricles are not contracting efficiently and synchronously.  The left ventricle is depolarizing by way of a slow wave of depolarization, rather than all the cells getting the message to depolarize at the same time.  Having these two conditions at the same time can have a very negative effect on cardiac output, leading to CHF.  The first step in treatment often involves simply slowing the rate to normal, which allows for better ventricular filling and decreases the workload on the heart.  Then, the fibrillation and bundle branch block can be addressed.

Dawn's picture

Wide Complex Tachycardia

Submitted by Dawn on Sat, 09/14/2013 - 21:40

This ECG shows a wide-complex tachycardia with a rate of 137/minute.  No patient information is available other than what is on the ECG.  Here, we will comment for the BASIC LEVEL learner, and allow the ECG Gurus out there to add INTERMEDIATE and ADVANCED level comments.

Beginners and emergency workers should ALWAYS be cautioned to treat all wide-complex tachycardias as VENTRICULAR TACHYCARDIA until proven to be something else.  V Tach is a life-threatening dysrhythmia, and there should be no delay in treatment.  That being said, not all WCTs are V Tach.  The most common "mimic" of V Tach is left bundle branch block.  LBBB can appear along with any supraventricular rhythm, including sinus rhythms, atrial tachycardias, atrial fibrillation, and junctional rhythms.  The diagnostic criteria for LBBB are:  wide QRS (.12 seconds or more), supraventricular rhythm, negative QRS in V1 and positive QRS in V6 and Lead I.  This ECG meets the criteria for LBBB, except that the supraventricular rhythm is hard to prove.  On one hand, P waves are not seen - or at least not easily.  On the other hand, the ECG machine has recorded a PR interval and a P wave axis.  What do you think?

Some of the criteria that would favor the diagnosis of V Tach are not present here: precordial concordance (all QRS complexes in V1 through V6 pointing in same direction), V6 with a negative QRS, AV dissociation.  An extreme axis, especially extreme right, would favor V Tach.  This ECG has an abnormal left axis, which is possible in V Tach AND in LBBB.   For a more thorough discussion by ECG Guru Jason Roediger of the criteria for differentiating V Tach from LBBB and other aberrancy, go to this LINK.

In an emergency setting, WTCs are most often V Tach.  However, should the rhythm turn out to be SVT with aberrant conduction, the usual V Tach treatment protocols would do no harm.  For instance, if the patient is deemed to be "unstable", electric cardioversion is recommended for both V Tach and SVT.  If the patient is stable, the emergency drugs usually recommended are generally safe for both rhythms.

Care should be taken to differentiate SINUS tachycardia from SVT or V Tach.  Sinus tachycardia usually has an obvious physiologic cause (hypoxia, hypovolemia, fear, pain, fever, etc.).  Sinus tachycardia also will be variable in rate, slowing as the cause is alleviated, or speeding if the problem causing the tachycardia becomes worse.  It may require  a long period of observation to determine that the rate is gradually slowing or speeding up.  One would hope to find P waves at some point in sinus tachycardia, and a 12-lead ECG is a great help.

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Dawn's picture

Wide Complex Tachycardia: Left Bundle Branch Block With Subsequent Rhythm Strip

Submitted by Dawn on Sat, 06/22/2013 - 22:01

 This wide complex tachycardia has an initial rate of 129/min. It is difficult to discern if P waves are present, although the ECG machine does give us a PR interval. The ECG meets most of the criteria for left bundle branch block: wide QRS, negative QRS in V1, positive QRS in Lead I and V6.The axis is leftward, which is common in LBBB.  However, it is difficult to say for certain that this is a supraventricular rhythm. Later, however, the patient's rate slowed (see top strip), revealing P waves. When the rate slowed, the left bundle branch block pattern remained. That helps confirm the original interpretation of left bundle branch block. Interestingly, the BBB is not rate-related, in that it is still present at the slower rate.

Of course, it would be helpful to have a complete 12-Lead ECG after the rate slowed, and it would also be good to see the onset and/or offset of the fast rhythm, which would help to determine if this is a sinus tachycardia or a paroxysmal supraventricular tachycardia (PSVT).  We do not have clinical data to help us determine if a sinus tachycardia with a rate of around 130 / min. would be appropriate or expected in this patient.

Click on image, or, for best image quality, right click and SAVE image.

 

Dawn's picture

Spontaneously Changing Conduction In Wide Complex Tachycardia

Submitted by Dawn on Wed, 04/10/2013 - 22:23

This ECG was donated to the ECG Guru by Dr. Arnel Carmona, one of our favorite Gurus.  You will not often see such a great example of this.  We are very grateful to Dr. Carmona for his contribution to learning. Dr. Carmona's new blog is EZG - ECG for beginners and enthusiasts.    

An adult patient was admitted due to palpitations.  What is this rhythm?This is a tachyarrhythmia that initially is regular wide complex (RBB morphology) and later became regular narrow complex at a rate of about 187 bpm. There is normalization of the QRS without a change in heart rate. In the latter part of the tracing (narrow complex), pseudo-r can be seen in V1. So, this is SVT with aberrancy with spontaneous normalization.

What is the cause of the intraventricular aberration during acceleration of heart rate? It could be due to failure of the refractory period to shorten or possible lengthening in response to acceleration. 

What is the cause of the normalization of the of the QRS? The normalization of intraventricular conduction could be due to the gradual shortening of bundle branch refractory period in response to the tachycardia. 

Dawn's picture

Wide Complex Tachycardia: V Tach

Submitted by Dawn on Sat, 06/02/2012 - 14:02

This wide complex tachycardia occurred in a 91 year old man with a history of atrial fibrillation. He complained of "fluttering" in his chest, and denied chest pain or other problems.  While the paramedic attempted to start an I.V., he spontaneously converted to atrial fibrillation with left BBB, and PVCs.  Once he converted, his symptoms abated.  Remember, all wide complex tachycardias (WCT) should be treated as V Tach in the field, as this is by far the most common WTC and the most dangerous.

Some of the ECG clues that this WTC is ventricular tachycardia are:

* Monophasic upright QRS in V1  (does not have RBBB pattern of rsR')

* Extreme left axis deviation (II, III, and aVF are negative, I, aVL, and aVR are poisitive)

* V6 is negative

 

For a more thorough discussion of the ECG signs of V Tach, go to Jason Roediger's Ask the Expert page discussion on the topic:

http://www.ekgguru.com/node/157

Dawn's picture

Wide Complex Tachycardia in a Patient with WPW

Submitted by Dawn on Mon, 03/12/2012 - 16:03

This ECG was submitted by Sebastian Garay, EMT-P and ECG Guru (and ECG Guru Member sebmedic). It is a very interesting case of wide complex tachycardia in a patient with Wolff-Parkinson-White.

This is from a 57 year old man who sought medical help for a complaint of palpitations. He was known to have WPW. The paramedics determined that he was hemodynamically unstable, and in light of the wide-complex tachycardia, they performed a synchronized cardioversion at 100 j. The patient converted to the rhythm shown in the next ECG. The paramedics then administered a Lidocaine bolus and drip, considering this to be a ventricular tachycardia. The patient arrived in the Emergency Dept in improved hemodynamic condition.

This ECG can be used to teach V Tach for beginner students, WPW and WCT tachycardia differential diagnosis for more advanced students. It is also a good ECG for axis discussion, and for how lead placement affects the final product.

The differential diagnosis here is 1) V Tach and 2) SVT with aberrant conduction or left ventricular conduction delay. For a discussion of ECG criteria which help us diagnose WCT, see the "Ask The Expert" column from Jan. 11, 2012. Characteristics that make this look like V Tach include: wide complex and significant left axis deviation. Features which may favor a diagnosis of SVT are the pre-existing WPW and a rate of 222/min. There are no p waves seen. NOTE: V2 in this ECG appears to reflect electrode mis-placement, as it does not "make sense" in the normal progression of the QRS complexes in the precordial leads. It is clearly "out of place".

 

The second ECG shows the same patient after conversion of the tachycardia.  The delta waves of WPW are easily seen.

Dawn's picture

Wide Complex Tachycardia, 12 Lead ECG and Rhythm Strip

Submitted by Dawn on Wed, 11/30/2011 - 13:22

This is a good example of wide complex tachycardia that must be evaluated for V Tach vs supraventricular rhythm with left BBB.

There is an irregular rhythm.  When the rate is fast, it is important to look at a longer strip, as sometimes fast rates will cause the rhythm to look regular.  We know that monomorphic V Tach is not irregular, so that tells us that we are looking at atrial fibrillation.  

The ECG criteria for left bundle branch block is met here:  1) supraventricular rhythm (atrial fib), 2) wide QRS, and 3) negative QRS in V1 and positive QRS in Leads V6 and I.

With wide complex tachycardia, there is always a chance of ventricular tachycardia, and the patient should be treated as V tach until proven differently.  For more on determining whether a WCT is V tach or SVT with ventricular conduction delay, go to this LINK. 

Dawn's picture

Wide Complex Tachycardia: Left Bundle Branch Block

Submitted by Dawn on Wed, 11/30/2011 - 13:03

Today, we are revisiting an ECG from the archives, with a NEW comment from Dr Ken Grauer. This ECG is worth a second look because it is a very good example of the left bundle branch block pattern. It's also a good ECG to use when discussing treatment of wide-QRS tachycardias.

This ECG demonstrates a wide complex tachycardia with classic signs of LBBB: wide QRS, QRS negative in V1 and positive in V6 and Lead I, and supraventricular rhythm. P waves are difficult, if not impossible, to discern for sure. The machine does give a P wave axis and PR interval.  When evaluating a wide complex tachycardia, the patient's hemodynamic stability will initially determine treatment.  All WCTs should be treated as V TACH until proven otherwise.  The presence of a typical LBBB pattern makes LBBB very likely, but is not a sure thing.  This patient was confirmed to have LBBB when the rate slowed, the P waves became visible, and the QRS complexes did not change.

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