# V-Tach vs Paced rhythm



## Ginger Medic (Jul 30, 2015)

Hey all,

Transported a patient last night with abdominal pain to a local ER. On scene, patient was in uncontrolled A-fib between 106-110. 12 lead showed the same, no stemi or ectopy. At time of transport, patient was throwing intermittent runs of 3 complexes that looked like PVC's. Began our transport and printed a strip for documentation. On my call in, patient went into what looked to be a 10 second run of V-Tach. Hit print and noticed my Lifepak monitor indicating that there was a pacemaker active with the arrow icons, however, the monitor also was indicating there was a pacemaker within the A-fib complexes too. Does anyone know how to tell whether there truly was a run of V-Tach or just a paced rhythm? The patient did have a pacemaker history, however, it shouldn't be kicking in at over 100bpm...also, I could not see a pacer spike in my EKG strips. This and the fact that the monitor was seeing pacer spikes within some of the A-fib complexes leads me to believe the monitor was seeing what wasn't there. Also, patient had a significant cardiac and renal history which would preclude her for a cardiac event. Any ideas are appreciated.


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## cprted (Jul 30, 2015)

Does the patient have a pacemaker? If they don't have a pacemaker, I'd suggest they were probably not paced.

Most likely, the artifact from being in a moving vehicle made the LP think there were pacer spikes.


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## triemal04 (Jul 30, 2015)

Without looking at the strip hard to say for sure.  What was the rate of the run of abnormal beats?  It is possible with the afib that there was a period with a long enough R to R interval that the pacemaker kicked in, or conversely, if the rate had become fast enough (how fast depends on the individual person) it may have been attempting overdrive pacing, though that's less likely with a documented history of afib.  Or it certainly could have been a run of vtach.  The lack of pacer spikes doesn't mean much either.

Did the patient's presentation change before/after/during the event?  What else was going on besides abdominal pain?


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## Ginger Medic (Jul 30, 2015)

I unfortunately didn't take a picture on my phone and turned my strips in for documentation. The patient did have a pacemaker. The run was at the same rate as the A-Fib, about 100-110 (which is really slow for V-Tach, but hey). There was never a period where the rhythm dropped bellow 88, so if it was a pacemaker, it malfunctioned. Her presentation didn't change, though she was already complaining of dizziness and mild shortness of breath with pale skin signs. Her pulse was weaker at the radial site. GCS remained the same. I hear there is a way to tell through voltage criteria or something similar whether  a rhythm is paced or not.


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## RocketMedic (Jul 30, 2015)

Many pacemaker/AICD units are set to try and pace a person out of a lethal rhythm and will only defibrillate after a certain number of ectopic beats- ie 25.


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## Ginger Medic (Jul 31, 2015)

RocketMedic said:


> Many pacemaker/AICD units are set to try and pace a person out of a lethal rhythm and will only defibrillate after a certain number of ectopic beats- ie 25.



Interesting


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## ERDoc (Jul 31, 2015)

Were you looking at a rhythm strip or 12-lead?  Sometimes, if a pt is shaking their leg it can look like VTach.  If you have a 12-lead and only see "VT" in a few leads then it is not a true VT.  I'm not saying that is what happened here, but just a thought.


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## Ginger Medic (Jul 31, 2015)

This definitely wasn't just artifact...
	

		
			
		

		
	
















Pulled it from the PCR, excuse the low quality, but maybe this helps


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## triemal04 (Jul 31, 2015)

Paced.  The overall all rate doesn't determine when a pacemaker kicks in; it's the R to R interval.  Exactly how long it needs to be and for how long a period of time will vary, but with afib it is conceivable that it reached the limit while the lifepack still was "sensing" a rate of 100 or so.  For instance, on the 2nd to last strip it lists a rate of 174; not even close to what is actually happening.  (which brings up another point; with faster afibs, or even slower ones, don't go by what the monitor tells you if you want a more precise rate).  That same strip also shows an intrinsic beat pop up sooner than the pacer would have fired and terminate it working.

There are plenty of dual-chamber pacemakers out there, so some of the pacer arrows may be the result of that...or it's just the lifepack being a lifepack.


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## Ginger Medic (Jul 31, 2015)

I would think that too, but then you have to explain why it's still sensing a paced rhythm when the QRS has a normal morphology (in the second and third strips). If a pacemaker was firing, I'd think that it'd continue to show the same QRS. I'm not seeing it pop an intrinsic beat before the pace arrow...I'm seeing pacing arrows in line with the QRS. 

The R-R interval stayed the same throughout the transport. It once slowed down to approximately 90 after the run of possible VT/paced rhythm, but again, that was after the fact. My thought would be you'd see a constant pacing if it was the R-R interval causing it. This doesn't rule out that the pacemaker could be malfunctioning.

As for the rate, I realize that it never went to 174, that's the other thing that would indicate it was a paced rhythm because you can clearly see it's at approximately 100, however, you can still have a slow VT rhythm, it's just not the normal rate you'd expect. In the ER on their monitor, the patient did throw at least one PVC while I was turning over care without a pacer spike noted on the monitor. 

I've thought through all this during the call. I heard from another medic that there is a way using voltage criteria to tell if it's a pacemaker or not, so I was hoping someone here would be able to tell me how. The nurse I turned care over to seemed to think it was VT, but I'm still on the fence between the two due to all the reasons we've been discussing.


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## chaz90 (Jul 31, 2015)

Definitely a paced rhythm after seeing the rhythm strips. Look on the third image at the fact that the pacer kicked in with a demand pacing beat after there was too long of a pause from the intrinsic rate, then immediately shut off again when the intrinsic beat came back before the pacer's programmed R-R interval. That's clearly not a PVC as it's not premature. The LP is giving even more evidence by sensing (and filtering out) the pacer spikes itself.


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## chaz90 (Jul 31, 2015)

Ginger Medic said:


> I would think that too, but then you have to explain why it's still sensing a paced rhythm when the QRS has a normal morphology (in the second and third strips). If a pacemaker was firing, I'd think that it'd continue to show the same QRS. I'm not seeing it pop an intrinsic beat before the pace arrow...I'm seeing pacing arrows in line with the QRS.
> 
> The R-R interval stayed the same throughout the transport. It once slowed down to approximately 90 after the run of possible VT/paced rhythm, but again, that was after the fact. My thought would be you'd see a constant pacing if it was the R-R interval causing it. This doesn't rule out that the pacemaker could be malfunctioning.
> 
> As for the rate, I realize that it never went to 174, that's the other thing that would indicate it was a paced rhythm because you can clearly see it's at approximately 100, however, you can still have a slow VT rhythm, it's just not the normal rate you'd expect. In the ER on their monitor, the patient did throw at least one PVC while I was turning over care without a pacer spike



The "normal" looking QRS morphology are likely from a dual chamber atrial pacemaker as triemal suggested, or could be artifact and false pacer spikes. Atrially paced rhythms often look very similar to normal EKG morphology as the pacemaker is letting the impulse start in the atria and conduct normally through the ventricles, which is of course what the QRS is showing.


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## Ginger Medic (Jul 31, 2015)

chaz90 said:


> The "normal" looking QRS morphology are likely from a dual chamber atrial pacemaker as triemal suggested, or could be artifact and false pacer spikes. Atrially paced rhythms often look very similar to normal EKG morphology as the pacemaker is letting the impulse start in the atria and conduct normally through the ventricles, which is of course what the QRS is showing.



Makes sense, thanks for the help


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## chaz90 (Jul 31, 2015)

I've never heard anything about voltage criteria for paced rhythm determination either. Perhaps someone more versed in electrophysiology has, but I'm coming up blank with my Google-fu as well. 

Honestly, the concept doesn't make a lot of sense to me either. Voltage criteria shouldn't have much to do with where the initial impulse was started. You can have very low amplitude VT or other ventricular escape beats that are normally associated with higher voltages, and you can have crazy high voltage sinus rhythms with severe LVH originating from the SA node.


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## TomB (Jul 31, 2015)

This reminds me of Rhythm Challenge #5.

Part 1
http://www.ems12lead.com/2010/11/26/rhythm-challenge-5/

Part 2
http://www.ems12lead.com/2010/11/27/rhythm-challenge-5-answer/

In the bottom strips the pacemaker keeps firing but finds the ventricles refractory due to the native rhythm (sometimes called pseudofusion).

Tom


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## triemal04 (Aug 2, 2015)

Ginger Medic said:


> I would think that too, but then you have to explain why it's still sensing a paced rhythm when the QRS has a normal morphology (in the second and third strips). If a pacemaker was firing, I'd think that it'd continue to show the same QRS. I'm not seeing it pop an intrinsic beat before the pace arrow...I'm seeing pacing arrows in line with the QRS.


Could be due to the type of pacer as I said, or possible due to it being a Lifepack; this may be true with most monitors since most use the GE/Marquette software, but the LP's will on occasion "sense" a pacemaker where one doesn't exist.



> The R-R interval stayed the same throughout the transport. It once slowed down to approximately 90 after the run of possible VT/paced rhythm, but again, that was after the fact. My thought would be you'd see a constant pacing if it was the R-R interval causing it. This doesn't rule out that the pacemaker could be malfunctioning.


Not exactly.  Pacemakers (unless someone puts a magnet on it) function on a demand basis; if the intrinsic heartrate is fast enough the pacer will turn off and allow the heart to beat naturally.  How fast depends on the specific person and what their settings are.

Also, take a look at the 4th strip that only has one paced beat on it.  If you look at the preceding R wave and count it out to where the pace kicks in, that R-R interval corresponds to about a rate of 80-90; it's slower than the preceding beats and low enough that the pacer needed to kick in.  If you look at the R-R from the paced beat to the next normal beat it's at about 100; faster than the pacer would fire, so it shut down and let the heart beat normally.



> As for the rate, I realize that it never went to 174, that's the other thing that would indicate it was a paced rhythm because you can clearly see it's at approximately 100, however, you can still have a slow VT rhythm, it's just not the normal rate you'd expect. In the ER on their monitor, the patient did throw at least one PVC while I was turning over care without a pacer spike noted on the monitor.


The rate of 174 just means that with afib monitors aren't the best at giving accurate rates.



> I've thought through all this during the call. I heard from another medic that there is a way using voltage criteria to tell if it's a pacemaker or not, so I was hoping someone here would be able to tell me how. The nurse I turned care over to seemed to think it was VT, but I'm still on the fence between the two due to all the reasons we've been discussing.


He's probably talking about using a 12lead to check to criteria to rule in/out vtach versus a wide complex rhythm of other origins. 

Trust me, this was a paced rhythm not vtach.


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## Melbourne MICA (Aug 5, 2015)

Ginger Medic said:


> This definitely wasn't just artifact...
> 
> 
> 
> ...




Hi All,
A couple of things I noticed. The rhythm is not regular in all three strips. All the strips have a lot of artifact. If you can clearly see P waves in all the strips you have better eyes than me. Too much artifact. Assuming you can measure, as I did, by checking the regularity of the rhythm on the computer monitor with a piece of paper and pencil marks, the QRS in the aberrant section under discussion is wide but less than 3 sqrs so probably not VT - rate too slow as well. There are no discernible P waves. The rhythm is <100bpm (measure it - I did). The rhythm is definitely irregular in all 4 strips ( checked it with paper and pencil against the screen). I can't see any pacing spikes. So my two bobs worth? A run of ectopic beats overlying an Afib with a BBB probably L (no v leads and no AVL/AVF to look at). Looking at the last strip, in between artifact there looks to be an RSr pattern (suggests BB as well). We don't know what type of pacemaker do we? Did I miss it? Demand or non-demand? Does the pt have the pacemaker for afib? Not unusual to have one for this purpose - same pts are often on amiodarone now for Afib as well. If the rate isn't above the threshold for the pacemaker (100bpm?) and its a demand variety then it won't kick in which would explain no spikes. Most Afib management these days is rate control oriented if permanent reversion is not possible. Hence anti-arrhythmic and pacemaker.

Melbourne MICA


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## johnrsemt (Aug 16, 2015)

Ask the patient if they have a pacemaker:  I have had my monitor tell me it was a paced rhythm when they said they didn't have a pacemaker, and so did the husband and daughter and the ED doctor after some quick research.  Wow treatment in the ED changes when everyone realizes it really is V-tach and not just a funky paced rhythm


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