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Wenckebach conduction

Supraventricular Tachycardia With Wenckebach Conduction

Wed, 03/16/2016 - 22:55 -- Dawn

This ECG was obtained from a patient in a walk-in health clinic.  We do not have any other information on the patient.  We thank Joe Kelly for donating this interesting ECG to the GURU. 

IRREGULAR RHYTHM    If you march out the P waves, you will see that they are regular, at a rate of approximately 130 bpm.  But the QRS complexes are not regular, and there are fewer QRS complexes than P waves.  

WENCKEBACH CONDUCTION   Looking closely at the PR intervals, you will notice that they progressively prolong.  This “pushes” the QRS complexes progressively toward the right.  Eventually, the T wave – and the refractory period – will land on the next P wave.  That P wave will be unable to conduct to the wave, and no T wave of course, so the next P wave will conduct with a shorter PR interval.

We are including a short rhythm strip from this patient, with conduction marked with a laddergram. 

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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Atrial Flutter With Variable Conduction

Tue, 11/04/2014 - 00:24 -- Dawn

This ECG provides an example of atrial flutter with variable conduction.  There are two distinct R - R intervals, making this a somewhat regularly-irregular  rhythm, as opposed to the irregular irregularity of atrial fibrillation.  The flutter waves (P waves) are very easy to see in most leads, but not in all.  If you are teaching students who are making the transition from reading monitors and rhythm strips to 12-lead ECGs, this is a great ECG to illustrate for them how the more leads you have, the more you will see.  The flutter waves are invisible in Lead I and, to the untrained eye, they may be hard to see in the precordial leads.  The four channels on this ECG are run simultaneously, so if  P waves or flutter waves are visible in one lead, they are also present in all leads that line up vertically with that one.  In other words, the Lead II rhythm strip at the bottom confirms that flutter waves exist across the entire ECG.

The R - R intervals in this ECG reflect alternating 2:1 and 4:1 conduction.  There are a couple of times when the 4:1 ratio repeats itself without alternating.  Often, the length of these varying R - R intervals will be multiples of each other, or have a common denominator.  These do not appear to, and may reflect the fact that, when R to P intervals lengthen, R to R intervals sometimes shorten.  In other words, the PR intervals, which are difficult to measure in atrial flutter, may be changing.  I would invite my colleagues with more expertise in this area to comment below.

There are no blatant ST segment abnormalities here, but ST segments can be very difficult to assess in atrial flutter because of the flutter waves.  We do not have clinical data, other than this is a 62-year-old man.

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