This is the discussion for 60 year old male CC: "I don't feel well".
Go back and familiarize yourself with the history and clinical presentation because it's important to the case (as it always is).
Here is the rhythm strip and 12-lead ECG that was presented.
You may recall from my series on ineffective or inappropriate ICD shocks rhythm analysis for patients with an implantable cardioverter-defibrillator can be challenging.
That's because patients with sick hearts often suffer from both atrial fibrillation and bundle branch blocks which predisposes them to "wide and fast" rhythms.
If you've taken nothing else away from the EMS 12-Lead blog I hope you've taken away the message that "wide and fast" is VT until proven otherwise!
Granted, irregular wide and fast rhythms are a special case. In the first place you avoid adenosine according to the 2010 AHA ECC Guidelines. That's because atrial fibrillation is unlikely to respond to adenosine, not to mention that giving adenosine to a patient with WPW and atrial fibrillation can precipitate VF.
So let's look at the differential diagnosis of the wide complex tachycaria.
Could it be VT?
Sure. It's rare for VT to be irregular but it's certainly not impossible. We need to remember that the patient has received an ICD so one assumes the patient is at high risk for malignant ventricular arrhythmias. "But the axis is normal!" you might say. Yes, but as I've mentioned so many times before, it's an EMS myth that VT always shows an extreme axis deviation. In fact, LBBB in lead V1 with a normal frontal plane axis is normal for VT orignating in the right ventricular outflow tract.
Could it be AF with LBBB and RVR?
Yes. This is entirely possible. Quite often irregular wide complex tachycardias turn out to be AF with RBBB, LBBB, or nonspecific IVCD. It's a bit unusual but certainly not impossible for LBBB to show a normal frontal plane axis.
So, if it could be either VT or "SVT" (a term I don't care for) with aberrancy (or preexisting bundle branch block) then how should we treat the patient? Should we treat the patient at all?
When faced with a situation like this I think it's far more important to "risk stratify" the tachycardia rather than "diagnose" it. In other words, remember the first rule of medicine: "Do No Harm!"
Above all else, avoid IV medications that could kill the patient if it turns out to be VT.
So why isn't the ICD shocking? Because the rate isn't fast enough. It's not unusual at all for patients with an ICD to present with a wide complex tachycardia below the rate limit that initiates cardioversion or defibrillation.
So what else happened in this case?
En route to the hospital an additional 12-lead ECG was captured and several more rhythm strips.
This 12-lead ECG reveals an important problem with prehospital 12-lead ECGs. They often crop the S-wave, especially in the right precordial leads (V1-V3) which can makes it impossible to compare the ST-segments to the depth of the S-waves (rule of proportionality).
The patient was delivered to the emergency department where the following 12-lead ECG was taken.
Now we can see the depth of the S-waves in leads V1-V3 and there's a problem (beyond the fact that the precordial leads have been placed differently on the patient's chest).
If this is a left bundle branch block then excessively discordant ST-elevation is present in leads V2 and V3 which indicates acute STEMI.
So what was the outcome?
All we know for certain is that the patient received successful synchronized cardioversion in the emergency department. The paramedic who submitted the case was told by the RN in the emergency department that the QRS complexes were narrow after the cardioversion (which would support a ventricular origin). However, we don't have a post-cardioversion 12-lead ECG to confirm.
We also don't know whether or not the patient ruled-in for AMI. But I certainly wouldn't be surprised!