Not a Good Thing

It’s how my A&P professor used to classify the problems that could happen to the human body.  It was either OK, or not a good thing.  I’ve learned all sorts of things that surely fall into the latter category, hell, we see that all the time.  Then there times where you foresee the worst possible, but the reality is that it isn’t that bad.  All things considered.

Case in point.  Complete (3rd degree) Atrioventricular [Heart] Block.  Just saying makes my heart rate speed up a bit.  All sorts of bad situations run through my mind.  The ACLS algorithim for bradcardia and PEA jump to the forefront of my memory as I see it pop up on the monitor screen as the “Oh SHIT!” alarm starts ringing for bradycardia.  You run into the patient’s room and they’re sitting there, alert, talkative and having a fine time.  “Do you feel weird?” I ask.

“No, why?” he says.

“Your heart is doing something funny.  Sure you feel OK?”  I continue.

“Oh, that,” totally nonplussed,  “Naw it happens all the time.  I’m used to it.  That’s why I’m getting a pacemaker tomorrow.”  he finishes.

Then I remember the words of my EKG teacher:  sometimes we treat the monitor, others we treat the patient.  The key is to figure out which one is which.

So here’s the first strip:


Atrial rate: 80’s
Ventricular Rate: 60’s
Notice how the P-waves march through without any regard to the QRS complexes, except in beats 2 & 6.  Beat 6 appears to be preceded by a compensatory pause, where the conduction system appears to reset.  One could argue that this may be an extreme case of 1st Degree AV Block, but if you measure the P-P ratio you can see the march of the P’s, into and through the QRS complexes.  While it’s not a complete block, as some impulses do seem to carry through and you do have some time spent in sinus rhythm that I couldn’t scan in, you can tell the conduction system in not well.

Now a second strip:


Again, the atrial rate is in the 80’s, and the ventriclar rate is inthe 50’s.  Notice how the overall strip seemes to be stretching out, or slowing down.  The 5th beat is a PAC, but again, no reset happens.  After that you have a lone P-wave followed by a second P-wave with no QRS to be seen.

Pretty much in this case, the atria and ventricles are not working together at all.  At times there appears to be some synchrony, but whether that is coincidence can’t be seen in short rhythm strips like this.  For some reason I really dig on the heart blocks.  Some of my colleagues have a hard time getting their heads around the concept, but it makes perfect sense to me.  The short of it is that the top of the heart and the bottom are not communicating effectively, kind of like a dysfunctional family, or couple.  (really, AD’s description of the heart blocks is both incredibly informative and hilariously funny, but it makes so much sense.  Maybe I just have a dirty mind though.)  By the time you get to 3rd degree (or complete) heart block, the atria just does its own thing, usually clicking along at the normal rate for the SA node (60-100 bpm) while the ventricle clips along at its own rate, usually either junctional (40-60 bpm) or idioventricular (20-40 bpm).  The ventricular rhythm is determined by which escape pacemaker site is supplying the impulse, the AV node or  the His-Purkinje system.

In cases where the patient is asymptomatic, the are several things nurses can do.  First, keep them on tele for crying out loud.  Don’t let them leave the floor without an ACLS certified nurse.  You say, “Well, duh.”  To which I say, “You think this hasn’t happened?”  Second, either have transcutaneous pacer pads on the patient, or at the very least at the bedside.  Third, make sure they don’t get any nodal blocking agents, like metoprolol or diltiazem.  Once again, “Well, duh.”  Again, “You think, aww screw it…it has happened.”  Fourth, make sure they have at least 1 IV site, that works, preferably 2.  Finally, make sure Cardiology is involved as the ultimate fix is a permanent pacemaker.

Lucky for us the gent in question stayed hemodynamically stable through the night and ended up getting a new brigh and shiny pacemaker implanted the following morning.  It could have been far worse, for sure.

Emedicine’s article:  Heart Block, Third Degree

The ECG Blog has a great couple of case studies of this phenomenom, complete with 12-Lead tracings.  The latest, Complete (Third Degree) Atrioventricular Block with Junctional Escape Rhythm, is pretty darn cool, and it has our most common complaint in folks with this, “tiredness.”  Classic.

Dedicated to Sidney Sinus Node and Viginia Ventricle…



  1. Hey! Great case presentation here. In the upper strip, the AV block is not complete, as you say. This is Advanced/High Grade AV Block with Junctional Escape Rhythm. The reason it is not a complete block is that, as you have pointed out already, some P waves are not blocked and get conducted through the AV Node. A third degree AV block of this kind if called a High Grade or Advanced Third Degree AV Block. It seems that (counting from the left) QRS number 3 and 6 is preceded by a P wave that gets conducted through the AV Node. The conduction is blocked to a first degree (1AVB), as the PR interval is 180ms.

    High grade 3AVB is usually used to describe a conductoin block that is somewhere between 2AVB and 3AVB, and where at least two consecutive P waves are blocked. This is not the case in the upper strip, but the term High Grade Block is also used for rhythms that wander between blocked P waves and complete block.

    The second strip though, has two consecutive P waves being blocked and looks more like a high grade block.

    In both strips, I’m having trouble marching out the P waves (I’d love a scan with high res for zooming into..!:-), but it seems that the PP interval in the second strip is not regular. This could be Wenckebach Conduction out of the Sinus Node, but I am not sure..

    Anyway, you really got me excited here. I love heart blocks!

    Thanks for linking to my blog!

    – PQRST


    1. Wish I had better strips. I found these when I was cleaning out my bike bag so they had been living there for some time. No high-res available unfortunately, and I only have access to rhythm strips, a 12-lead would have been more helpful. I was considering the idea of Wenckebach as well, but it’s hard to tell as the P-waves merge with the QRS complexes so it kind of becomes a chicken vs. egg situation. Fun stuff no doubt though.


  2. I could actually make a argument for Wenckeback for the first strip with a dropped beat perhaps after the first, and then before the 6th, rather than a compensatory pause. I actually think there is a better case for this based on this strip than 3rd degree, with better evidence of a ever widening pr interval than buried p’s. I also would expect to see wider qrs’s with true 3rd degree as the ventricular rate is originating from the ventricles.

    While I love heart blocks I have learned to hate 3rd degree. There has never been a single case of 3rd degree that I have called that a cardiologist hasn’t called Mobitz II the next day.


  3. @Christine. I rest my case. Your observation is correct. I was talking about Wenckebach out of the SA Node, but I think you are correct that this is a 2AVB, type 1 (Mobitz 1) with Wenckebach conduction.

    With WB conduction the PR interval should be progressively prolonged, while the RR interval should be progressively shortened, until a P wave is blocked/dropped. Also, the RR interval containing the blocked P wave should be shorter than the sum of two PP intervals. All these criteria seem to match here.

    The second strip though, has an interval of two dropped P waves, and does not match the overall criterias for Mobitz 1/Wenckebach. I can’t really manage to march out the P waves here, but this is more likely to be a high-grade 3AVB, don’t you think?

    @Wanderer: This is such a great case. I envy you those strips! Can’t believe you just had them lying around in your bike bag! You should frame them on your wall! 🙂

    This actually seems to be the case here.

    Also, with WB,


  4. @ Christine: Regarding your 3AVBs that usually end up as 2AVB. Take a look at my blog. There are a couple (I think) 12-lead cases of complete 3AVB (full AV-dissociation).


  5. Yes, I’m a bit lucky. We see such odd stuff sometimes on my floor that I have to print strips to add to the collection. This one I printed months ago, then forgot it. I usually pick up one of two a month. It is a tele floor, this is our stock in trade.

    I’m inclined to agree with the high grade block as well. Interpretation really is more of an art than a hard and fast science, as evidenced by Christine’s comment that her 3AVBs seem to mutate into 2AVBs. But when in doubt, I say leave it to the cardiologist. As nurses we just have to deal treat the patient if need be, but it is a good idea to understand what it is we’re really dealing with it, if nothing more than to give it a name. Besides, I don’t think the cards guy really want to call it 3AVB, it’s too scary…


  6. You are right in that the label that we give the rhythm means almost as little as the squiggles do if the patient is asymptomatic. If they are symptomatic there is no time to argue over whether the PR lenghthens before the beats drops or not- they just need attention.

    However, it is fun to argue about after the fact, isn’t it?


  7. Working in a tele floor, I admit we do get too excited about 2AVB and 3AVB at times. We look at the monitor, stare at it, without checking the patient first.

    After 6 months of being a tele nurse (YUP it took me that long), I’ve learned to immediately check the patient first, check vitals, and then recheck the monitor. I then do what needs to be done–like put the pt. on 02, get a stat EKG, call the MD, and/or have the external pacer on standby depending on how symptomatic the patient is, and how slow the heart rate is.

    Great post.


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