I agree with general assessment by Dawn of this interesting tracing.

We see an almost precisely regular WCT (Wide-Complex Tachycardia) at a rate of ~140/minute. I say "almost precisely regular" - because I believe there are some very small irregularities in this tracing. I say this after measuring multiple times .... (something I'd never have the luxury of doing if this patient was in front of me! ). I don't think the tiny irregularity I detect is enough to call this AFib - and both AFlutter and VT may have some irregularity - so this is really not helpful to our differential diagnosis.

• I don't see P waves. I initially thought I might be seeing flutter waves in aVR - but with calipers set at half the R-R interval - these just don't march out.

So we are left with a regular (at least almost regular) WCT rhythm without evidence of sinus P waves. Since we don't know the history or clinical condition of this patient - we have to speculate:

• IF the patient was unstable - immediate cardioversion would be in order regardless of the etiology of this rhythm.
• That said, at a rate of ~140/minute - there is an excellent chance this patient might be hemodynamically stable regardless of what the rhythm is.

I've written up a similar case with step-by-step description on my ACLS Comments #11. GO TO: https://www.kg-ekgpress.com/acls_comments-_issue_11/ - The most important points to make about this tracing (assuming the patient remains hemodynamically stable) are the following:

• Assume VT until proven otherwise. Treat accordingly. But since the patient is stable - immediate cardioversion is NOT needed at this time.
• Even though statistically 8-to-9 out of 10 patients with a regular wide tachycardia will be in VT- I see NONE of the diagnostic criteria for VT on this tracing. There is no extreme axis - no monophasic R wave in aVR - no entirely negative deflection in lead V6 - and no obvious delay in initial QRS activation. Instead, I see a QRS morphology that looks exactly like LBBB (Left Bundle Branch Block).
• Therefore - while telling myself that I have NOT yet "proved" this isn't VT - I suspect it may not be.
• ACLS Guidelines now recommend giving Adenosine as the 1st drug for treatment of a regular WCT rhythm of uncertain etiology. While I would not necessarily do this if I was relatively confident the rhythm was ischemic VT - this particular case is PERFECT for a diagnostic trial of adenosine. Adenosine is unlikely to be harmful if the rhythm turns out to be VT (because of its ultra-short half-life). If the rhythm turns out to be an SVT - then Adenosine may convert the rhythm if it is AVNRT - and it may transiently slow the ventricular response for other forms of SVT, thus allowing definitive diagnosis to be made. I strongly suspect that an answer to what this rhythm is would be forthcoming following administration of Adenosine.

BOTtOM LINE: You do NOT have to be certain of the rhythm diagnosis at the time you initiate treatment. This is one such case in which I don't think there is any way to be certain before beginning treatment. As long as you remain ready to cardiovert at the first sign of patient deterioration - it is perfectly appropriate to proceed with Adenosine as an initial drug given as a diagnostic/therapeutic trial.

P.S. This might be a time to try an additional monitoring lead such as a Lewis Lead. This rhythm could be AFlutter - and use of a Lewis Lead might demonstrate flutter or other atrial activity.