This is the discussion for our "Snapshot" case, 58 year old male CC: Epigastric pain. You may wish to review the case before continuing.
Thanks to all of you, we had a lot of great comments!
Many of you had wished we had a rhythm strip to analyze… keep in mind, this 12 lead is a continuous ten second strip, long enough to analyze the rhythm. Learning how to interpret rhythm off of a 12 lead is a good skill to have!
So, let's review the 12 lead:
So what do we know? We have a bradycardic rhythm with a rate of about 36. There are visible P waves. The comments were mostly split between 2nd degree AV block type 1 (Wenckebach) , 2nd degree AV block type 2 (Mobitz II), and 3rd degree block (CHB). So, which is it? One very important thing to remember about 2nd degree blocks type 1 is that they will be irregular due to the dropped QRS. In this strip, some considered that there may have been a lengthening QRS and dropped beat, leading to a conclusion of Wenckebach. However, if you map out the QRS complexes, they are regular. That pretty much eliminates 2nd degree type 1. There is no constant PRI, which would eliminate 2nd degree type 2 from the differentials, and that leaves 1st or 3rd degree blocks. At that point, it becomes apparent that it is a 3rd degree block. Rhythms like this can be tricky, unless you look for all of the P waves. In this case, they are easiest to see in V3 and V4. You should get used to marching them out. You will find that many are "hidden" in T waves and just after the QRS complex, and may be missed unless mapped out, as I've done below:
The other interesting thing about this rhythm is that the QRS complexes are not wide, as we might expect, but narrow. What does this mean? It means that the escape beats are not coming from the ventricles, but from the AV node or high in the HIS system. As we know, these beats will perfuse much better than ventricular beats, and no doubt helped this patient remain more stable.
Next, we have to ask a question: Is the complete heart block is the primary problem, or secondary to something else? Most of you recognized the inferior STEMI, with ST elevations in the inferior leads, and reciprocal depression in leads I and aVL. Also, notice the ST depression in leads V1-V4. This is not reciprocal depression, but rather posterior involvement as well! So we have an infero-posterior STEMI, with probable RVI. You could do a 15 lead, but if you don't, he is already going to the cath lab:
A few things to keep in mind:
- Patients suffering an IWMI often present with epigastric discomfort or burning.
- As the RCA usually supplies the SA and AV nodes, AV blocks and bradycardias are common.
- IWMI often extend to the RV and posterior portions of the heart.
The last thing to discuss is how we would treat this patient. What about atropine? As was mentioned, atropine is not usually indicated in high degree heart blocks. However, if the escape is coming from the AV node, atropine could possibly be effective, but not likely. I'm not sure the unapposed sympathetic response is what we are after in this case anyway.
How about pacing? Same issues, plus the discomfort of the electrical therapy. Our patient is mentating well, and while his pressure is not very high (92 systolic), it is not terrible either. Fluids would be a good option here, and I think i would hold off on pacing unless he was shocky and the fluids didn't help.
It is important to remember that memorizing the ACLS algorithm is quite a bit different from applying it to our patients. We have to decide what the primary problem is and what will fix it. In this case, the primary problem is an occluded artery, which needs to be opened immediately. The arrhythmia is secondary to this problem, not the other way around. Some of are teetering on the edge, and the wrong treatment could push them over. We must always balance the benefit we expect from our treatment against the risk of what could go wrong if we do it. Is it worth it? Is it in the best interest of our patient? For this reason, we may decide not to give meds or pace, even though it could be justified under the "algorithm".
Unfortunately, we don't have any follow up or additional information to wrap this case up. But I can tell you this: Patients are complicated. Much more complicated than algorithms. We face grey areas and decisions that are not always easy. That is what makes medicine so interesting… and challenging.
We hope you enjoyed this interesting case. Thanks for reading, and keep up the good work!