Here’s the scene.
Six EM docs standing in the resuscitation bay staring at an EKG hotly debating the correct interpretation of the patient’s EKG after the patient becomes acutely tachycardic.
No. No. Wait. Let’s rewind.
A 50 y/o M PMHx HTN, DM, ESRD on HD, paroxysmal afib, on a truckload of medications rolls into the resuscitation bay presenting with one day of progressively worsening SOB. Compliant with HD (last session two days ago). Patient is ill appearing, but hemodynamically stable. Patient mentating well.
Suddenly, his heart rate on the monitor jumps to the 180s. The astute resident throws on pads and obtains this EKG. Presumed hyperK treatment is started.
What’s the arrhythmia?
Following this algorithm, we run into some snafus.
https://coreem.net/core/a-simplified-approach-to-tachydysrhythmias/
Is the QRS complex wide?
The machine reads the QRS ~121, which by the above algorithm means the QRS is wide. And while V4-V6 seems narrow, the limb leads are less convincing. Okay, it’s.. wide-ish.
Is the rhythm regular?
At a glance? Yes, totally looks regular. Marching it out on paper and using the “fold the paper” trick (https://emupdates.com/how-emergency-clinicians-determine-regular-vs-irregular/), it was less clear. Our ticks on the paper did not line up perfectly (sowing the seeds of doubt...)
Okay, let’s say it is a wide-complex regular tachycardia -- is it SVT with aberrancy or VTach?
There are a number of criteria designed to help with exactly this (Brugada, Griffith, Lau, Vereckei, Pava) with the popular being Brugada, but even with the Brugada algorithm let’s say we got stuck on Step 4 of those criteria “Morphology of VT” as we were not entirely sure if it fit or didn’t fit. Won’t dive into this part further as it has beautifully written up in the links below.
https://rebelem.com/svt-aberrancy-versus-vt/
https://litfl.com/vt-versus-svt-ecg-library/
Plus, the data is not great for ED physicians, and our accuracy with these algorithms (https://www.mdcalc.com/brugada-criteria-ventricular-tachycardia#evidence)
Also, remember in the SVT vs VT debate, rule of thumb is to treat as VT until proven otherwise.
So now what?!
Realistically, most of you may already have strong opinions on what this rhythm is (especially if you went through the above links) but let’s say you have adrenaline pumping in your system, you didn’t have time to carefully go through criteria, or you were handed an EKG that was more confusing than this one.
The question I asked myself was --
Can adenosine help us figure out the diagnosis?
And the important secondary question, is it safe to use?
Narrow QRS Complex + Adenosine: All Good
Adenosine is fairly safe to use in narrow QRS complex tachycardia. If SVT, it may terminate the tachycardia. In atrial fibrillation or atrial flutter, it may aid in identifying underlying P-waves or unmask otherwise not visualized flutter waves. We’re used to using adenosine in SVT. Old news. Below is a lovely chart with all the effects adenosine has on narrow complex tachycardias.
Let’s get to the good stuff. When should we use adenosine in wide complex tachycardia?
Wide QRS Complex, Regular + Adenosine: All Good
As per the current AHA Tachycardia With a Pulse Algorithm, we should consider giving adenosine if the rhythm is regular and monomorphic. Wait, is that true? Let’s look at each diagnosis one-by-one (and give them each a dose of adenosine)
SVT with aberrancy (+BBB, +WPW) - Great! You’ve treated the SVT. If the “aberrancy” is a bundle branch block, then you have treated the SVT as you would any other time. If the aberrancy is WPW but the rhythm is regular, congrats! You’ve blocked the limb of the re-entrant rhythm which goes through the AV node and interrupted the circuit. What a great doctor, you.
Ventricular Tachycardia - For most types of ventricular tachycardia, adenosine will do nothing. It has a very short half-life. The rhythm is being generated from below the AV node so an AV-nodal blocker will have little effect. However, there are adenosine-sensitive VTs (fascicular VT, RVOT VT) in which case you may actually break the VT with the adenosine. Which means you may miss the VT diagnosis by “accidentally” fixing the rhythm with adenosine, but realistically the patient will have further cards work-up and close follow-up regardless.
Wide QRS Complex, Irregular + Adenosine: No, no, no
Ventricular Fibrillation - If you’re taking the time to give adenosine to patients with Vfib, then we need to be having a whole other conversation. Shock, please.
Torsades - Mg! Adenosine can worsen things. There are case studies of adenosine-induced torsades in patients with long QT.
Atrial Fibrillation with Aberrancy - Very dangerous to give these patients adenosine. While other AV nodal blockers are more dangerous (CCB, beta blocker, digoxin), still not advisable to give adenosine. An AV nodal blocker will increase the conduction rate through the bypass tract and results in ventricular fibrillation.
Bottom Line:
Remember (quoting the great Dr. Steve Smith) any fast rhythm which worries you may be treated with electrical cardioversion. If confused, use electricity. If the patient is unstable, use electricity. All patients should be on pads before administration of any pharmacologic agent in case of hemodynamic collapse.
In stable patients not requiring immediate electricity, AV nodal blockers (like adenosine) are contraindicated when there is atrial fibrillation with WPW which have polymorphic QRS’s, irregular rhythms, and very short R-R intervals.
In all other tachydysrhythmias, adenosine is considered safe and can be a useful tool in diagnosis and treatment.
As long as the rhythm is not wide and irregular, adenosine can be trialed!
So what happened to our patient?
Patient looked decompensated. Got electricity. Went back to NSR. The end. Maybe we’ll try adenosine on the next one.
Sources:
https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-the-diagnosis
https://www.uptodate.com/contents/wide-qrs-complex-tachycardias-approach-to-management
https://www.uptodate.com/contents/narrow-qrs-complex-tachycardias-clinical-manifestations-diagnosis-and-evaluation
https://rebelem.com/svt-aberrancy-versus-vt/
https://litfl.com/vt-versus-svt-ecg-library/
https://www.mdcalc.com/brugada-criteria-ventricular-tachycardia#evidence
https://litfl.com/wide-complex-and-troublesome/
https://coreem.net/core/a-simplified-approach-to-tachydysrhythmias/
https://emupdates.com/how-emergency-clinicians-determine-regular-vs-irregular/
http://hqmeded-ecg.blogspot.com/2020/06/a-very-fast-wide-complex-tachycardia.html
https://hqmeded-ecg.blogspot.com/2016/03/wide-complex-tachycardia.html
http://hqmeded-ecg.blogspot.com/2011/10/wide-complex-tachycardia-ventricular.html
http://hqmeded-ecg.blogspot.com/2011/05/wide-complex-tachycardias-2-cases-what.html
Marill KA et al. Adenosine is safe and effective for differentiating wide-complex supraventricular tachycardia from ventricular tachycardia. Crit Care Med 2009 Sep 37:2512.
Link MS. Clinical practice. Evaluation and initial treatment of supraventricular tachycardia. N Engl J Med 2012; 367:1438. (Attached)
Tintinalli, Judith E.,, et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. Ninth edition. Section 3, 18 Cardiac Rhythm Disturbances New York: McGraw-Hill Education, 2020.