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ECG Challenge

ECG Challenge: Changing QRS Morphology

Sat, 11/12/2016 - 21:01 -- Dawn

Today's ECG CHALLENGE offers a two-lead rhythm strip and a 12-lead ECG from an 87 year old man with a complaint of shortness of breath.  We do not know any other clinical information.  What is the underlying rhythm?  How can we explain the changing QRS morphology?  There are two distinctly different QRS complexes - one wide and one narrow.  Comment below and let us know what you think.  We will answer your questions as soon as we can,  and will give a final diagnosis in one week.

ANSWER:  Please see Dr. Grauer's comment below for the diagnosis.  The intermittent left bundle branch block that is seen in this strip appears in the 12-lead ECG to be rate-related.  That is, after a PAC, we see a pause, and then normal conduction for one beat.  As the rate increases, the left bundle branch block resumes.  The rhythm strip, which was recorded about 5 1/2 minutes before the 12-lead ECG, shows more intermittent normally-conducted beats, which don't seem to be rate-related.  We would need a longer rhythm strip to definitively prove rate-related left bundle branch block, but it is a very common cause of intermittent LBBB.

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.

SEE THE INTERPRETATION AT THIS LINK

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