# 12 leads with paced rhythms.



## NomadicMedic (Aug 31, 2012)

I was just reviewing another medic's chart and he had a patient, let's say a 68-year-old female complaining of chest pain, non-reproducible not worse on inspiration or expiration. While he treated this patient with nitro and ASA, at no time did he ever perform a 12 lead.  When I asked him about it, he replied, "why would I do a 12 lead on a patient with a pacemaker?"

Facepalm. 

I was taught that you can use the Sgarbossa criteria to identify STEMI in a paced rhythm and serial 12 leads should be performed to look for ST segment depression and T wave inversion as well as provide a comparison for past ECGs. 

Has anyone dealt with this nugget, "no 12 leads with paced rhythm patients"?


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## sir.shocksalot (Aug 31, 2012)

We can not call cardiac alerts on paced rhythms, that being said, most physicians will listen and may call a cardiac alert on their own if you tell him/her that Sgarbossa's criteria are present.

I think a handful of paramedics will not do a 12-lead because of the view of "well I can't call a cardiac alert anyway so there is no point wasting my time to do a 12 lead".

My personal belief is that if there was a reason to put a patient on a 3 lead ECG then a 12-lead should be done every single time, it takes 20 seconds and can provide a much clearer view of what's going on.


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## STXmedic (Aug 31, 2012)

All the time. Drives me crazy. Or they see a LBBB and immediately crumple it up...


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## TomB (Aug 31, 2012)

You can use Sgarbossa's criteria but I would caution against using 5 mm of discordant ST-elevation as an activation criterion. LAD occlusion is a tough one for both LBBB and paced rhythm. At any rate, I agree 100% with the idea of establishing a baseline and looking for changes on serially obtained ECGs.


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## sir.shocksalot (Aug 31, 2012)

TomB said:


> You can use Sgarbossa's criteria but I would caution against using 5 mm of discordant ST-elevation as an activation criterion. LAD occlusion is a tough one for both LBBB and paced rhythm. At any rate, I agree 100% with the idea of establishing a baseline and looking for changes on serially obtained ECGs.


Yes! This! I don't know why I didn't mention this in my post. Serial 12-lead EKGs are really helpful when identifying MI, this is another reason to do a 12-lead on every patient that needs to be on the monitor.


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## NYMedic828 (Aug 31, 2012)

It takes me 30 seconds more to do a 12 lead.

I would say the medic was just lazy and looking for excuses.

The pacemaker generates the impulse but the heart still needs to depolarize to contract. The ECG is not all coming from a machine. 

When a patient is in asystole and has a pacemaker they may still have spikes but there is no complex. The complex changed due to the condition of their heart muscle function. 

I'm sure someone can find a picture of a major occlusion in a paced rhythm.


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## NomadicMedic (Aug 31, 2012)

I don't know if it's he's lazy or he just didn't know. I suggested to the education department that we do a Con Ed session on detecting EKG changes in paced rhythms.


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## MSDeltaFlt (Aug 31, 2012)

There's another reason why you'd want to do a 12 lead on your chest pain pt who has a caretaker.  Batteries have a limited battery life.  Wires can become disconnected.  Both of which can cause rhythm changes.  Never say never.  Never say always.  Get a 12 lead.


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## KellyBracket (Aug 31, 2012)

This is a great topic, since the world's literature consists of a handful of studies, and those studies deal with only a (relative) handful of patients! 

*Sgarbossa's study* from 1998 analyzed the ECGs of only *17* patients with ventricular-paced ECGs and postive enzymes. A *more recent study* looked at the ECGs of *58* patients. This does not make for a huge evidence base!

Nonetheless, both of those studies found that the "5 mm ST-discordant" rule was found to be very _specific_ for predicting AMI (by enzymes, not by angiography). A *third study*, however, did not find this criterion to be as helpful, given that so many baseline paced ECGs had the same degree of elevation.

This situation is rare, however. The second study I mentioned looked at all the patients over 6 years at 2 EDs with a combined volume of 170K pts/year, and only found those 58 patients meeting criteria. We aren't going to encounter this situation very often, thankfully!

Last thought: I wonder how we should look at the ECGs in patients with the biventricular pacers?


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## TomB (Sep 1, 2012)

No idea with regard to biventricular pacemakers. They can do some wild things with multi-site pacing. As for discordant ST-elevation the problem with Sgarbossa's criteria is that it did not take into account the depth of the S-wave (rule of proportionality). The Smith modification appears to be superior in every way (both sensitivity and specificity). ST/QRS ratio (measured at the J-point) of 0.2 is referred to as "excessive discordance". The rule of thumb I use is to round up to the number of large blocks of S-wave depth and that's how many mm of discordant ST-elevation I allow in that lead. So given a QRS with an S-wave that is 44 mm deep I would allow 9 mm of ST-elevation but not 10 mm. Or, if the S-wave is only 13 mm deep I would allow 3 mm of ST-elevation but not 4 mm.


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## TomB (Sep 1, 2012)

As a final thought, using patients with positive biomarkers is a fatal flaw because it groups together STEMI and NSTEMI and we're only looking to identify patients with an occlusive thrombus in an epicardial coronary artery. Smith's modification seems to do quite well at identifying LAD occlusion.



KellyBracket said:


> This is a great topic, since the world's literature consists of a handful of studies, and those studies deal with only a (relative) handful of patients!
> 
> *Sgarbossa's study* from 1998 analyzed the ECGs of only *17* patients with ventricular-paced ECGs and postive enzymes. A *more recent study* looked at the ECGs of *58* patients. This does not make for a huge evidence base!
> 
> ...


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## KellyBracket (Sep 1, 2012)

TomB said:


> ... The rule of thumb I use is to round up to the number of large blocks of S-wave depth and that's how many mm of discordant ST-elevation I allow in that lead. ...



Dang that's simple. Wish I'd thought of that.


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## Doczilla (Sep 1, 2012)

MSDeltaFlt said:


> There's another reason why you'd want to do a 12 lead on your chest pain pt who has a caretaker.  Batteries have a limited battery life.  Wires can become disconnected.  Both of which can cause rhythm changes.  Never say never.  Never say always.  Get a 12 lead.



Only a Sith deals in absolutes.....


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## MSDeltaFlt (Sep 1, 2012)

Doczilla said:


> Only a Sith deals in absolutes.....



May the Force AND the Schwartz be with you.


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