Here is the discussion for the Snapshot Case: 32 year old male–Chest Discomfort. Sorry for the delay.
If you recall, we have a young patient, a 32 year old male, with a heart rate too rapid to count. He is alert and oriented, and has a good pressure (126/70). He has been in the following rhythm for at least two hours:
So, what do we know about the rhythm? It is wide and fast, with a rate of 262. Since wide + fast = VT until proven otherwise, you couldn't be faulted for running it as VT.
Unfortunately as a "Snapshot Case", we don't know the outcome of this patient. However, our mission was to come up with a differential for this rhythm, so I'll share some thoughts:
- A-Flutter with 1:1 conduction: With rates approaching 300, it would be appropriate to consider it. I don't see any evidence of flutter waves though.
- SVT with LBBB aberration: The QRS is wide, but not that wide at 130 ms. V1 is negative, and there are monomorphic R waves in leads I and V6. This is typical morphology for LBBB. Also, let's look at a clear QRS, from lead III:
You can see that the initial downstroke of the QRS is sharp, and occurs in less than 20 ms. This as well favors SVT/LBBB over VT. If it is SVT, it could be either AVRT (WPW) or AVNRT.
- VT: The rhythm is wide and fast, and it is possible that this is VT. The QRS is not that wide but it could still be fascicular VT (but I would have expected RBBB morphology) or RVOT VT (which would not have RBBB, but then I would expect the inferior leads to be positive not negative). It doesn't seem to meet any criteria that rule in VT (no initial R wave in aVR, concordance, etc), but that does not rule out VT. And then there is the sharp initial deflection of the QRS, instead of a slower activation. And of course the patient's age and history do not favor VT.
All in all, I think any of the above are reasonable in this case. We can't know for sure, but I lean towards SVT with LBBB aberration, probably rate related, unless he happens to have LBBB as a baseline. You may have other thoughts, and I'd love to hear them!
As far as treating the patient, his mental status is good, his pressure is good, and he has been tolerating this rhythm for at least two hours. I think he's a good candidate for a trial of Adenosine, which might reveal the answer. If that fails, there is Amiodarone, cardioversion, or diesel as far as my protocols go.
With no clear cut answer, I'm sure you all will have some good thoughts to add to this discussion. Sometimes, we just don't know for sure, but we still have to hone our skills of considering our differentials.
Thanks for reading, and I'm looking forward to your comments!