When treating patients that have a regular, wide-complex tachycardia (WCT) focus on not being stupid rather than trying to be brilliant.
As much as we might think of ourselves as brilliant interpreters of ECGs, when the AHA states to "obtain expert opinion" on matters surrounding WCT, EMS is probably not who they had in mind. Many in EMS may have the knowledge, but lack the experience, and they lack the crucial component of feedback on our ECG diagnoses to be true experts. The feedback sanction surrounding our ECG diagnostic skills allows cognitive biases and faulty logic to not only exist but to flourish.
EMS providers are trying to play the winner’s game when assessing wide-complex tachycardias. That is the wrong approach. EMS (and probably everyone in health care without an EP lab at their disposal) should be playing the loser’s game.
The Loser’s Game: how a book about tennis will help you with ECG interpretation and life.
Simon Ramo wrote Extraordinary Tennis Ordinary Players. This book has profound ideas that can be used far beyond the tennis court.
Ramo explains that there are two strategies for winning a tennis match depending on how skilled the players are. The highly skilled players engage in a “winner’s game,” where they score points off their opponents. These skilled players win the match because they scored more points than their opponents using their skills and well-practiced techniques. They beat their opponents by being the better tennis player.
The average tennis player should not use a winner’s game strategy in a match, they should use the “loser’s game” strategy. To win using the loser’s game strategy, the average tennis player tries to make less mistakes than their opponent, they lose fewer points than their opponent does. They do not try to be fancy; they don’t try and beat their opponent with heroic shots across the court, they simply return the serve back to the opponent so their opponent can screw it up by hitting the ball into the net or off the court. They win by losing fewer points than their opponent does. This is the approach that EMS should embrace when dealing with WCTs. EMS needs to stop playing a winner’s game. EMS needs to employ a loser’s game with WCTs.
Nerds! I’m a reformed ECG nerd. Formerly insufferable about ECGs, pointing out axis deviations and rambling about the most trivial of details that no one cares about. I am in ECG-Nerd remission currently, but still relapse every now and then. I still love how each ECG is a puzzle to be figured out, a mystery to be solved or a cipher to be decrypted. But I try to stop myself from rambling on about the minutia before reaching the point of diminishing returns. For example, EMS has some weird obsession with doing posterior ECGS. If a patient has an obvious MI on the ECG, hunting for posterior involvement is a meaningless task—it does not provide any more useful information. If a patient is having a STEMI, finding that they are having “even more STEMI,” does not add anything of value to the clinical picture. It is ECG-nerdism at its finest. Any time someone tells you there is an MI with posterior involvement, ask them, “cool…so what?” And see what their answer is. I am all for doing a posterior ECG when an isolated posterior MI is suspected (even though a typical ECG is better at picking it up), but if you have already found the MI, please just stop there.
The older I get the more I appreciate efficiency. Taking a regular, wide complex tachycardia with no associated P waves past the point of calling it exactly that, a WCT, does not have any diagnostic yield. It is low-speed, high-drag.
We have to fight against the years of EMS cardiology programming in our heads, calling for us to go one step further than needed when presented with an ECG showing a WCT, telling us to “name the dog before it can bite you.” The truth is all dogs can bite you, just some harder than others. Their name doesn’t usually matter.
When faced with a pulsatile, regular, wide-complex tachycardia, strongly consider playing the loser’s game—just call it that and stop, go no further. Simply saying, “I dunno, it’s regular, wide and fast,” is all that is needed. There is nothing to be gained from stratifying a WCT into VT or SVT—the treatment is the same regardless of what we call it.
You cannot rule out VT.
There are no ECG rules or guidelines that can rule out VT when presented with a regular wide complex tachycardia with no P waves. Regardless of whatever you learned in paramedic school at or the latest edutainment CE you attended. That is so important it needs to be repeated: There are no ECG rules that definitively rule out VT when presented with a regular wide complex tachycardia.
The rule in/rule out fallacy Much confusion surrounding the diagnosis of WCTs comes from a simple misunderstanding; assuming that “ruling in” and “ruling out” are two sides of the same coin. The absence of a sign that rules in a condition does not mean the condition is ruled out. As the saying goes, absence of evidence is not the same as evidence of absence.
The absence of something that is believed to rule in VT, such as concordance in the precordial leads, does NOT rule out VT (also, it should be mentioned that concordance does not mean it is VT, only it is perhaps more likely to be VT if present.) Most signs and symptoms involved in ruling in/ruling out disease are not absolutes; they simply change the likelihood ratio of the disease.
Thinking in probabilities: more or less likely
The novice tends to think in binary terms. Either this x or y, either this is a WCT is VT or it is SVT. The expert thinks in probabilistic terms, using terms such as “more likely” and “less likely” and “probably” and “I think.” It is counterintuitive that with the more expertise you gain, the less certain you become of some things. In the realm of expertise, certainty is a rarity.
Thinking in probabilities: more or less likely
The novice tends to think in binary terms. Either this x or y, either this is a WCT is VT or it is SVT.
The expert thinks in probabilistic terms, using terms such as “more likely” and “less likely” and “probably” and “I think.” It is counterintuitive that with the more expertise you gain, the less certain you become of some things. In the realm of expertise, certainty is a rarity.
Ruling out VT is a dangerous game and should not be taken lightly. When any regular WCT is posted online a litany of opinions are offered and arguments are sure to break out in the comments section. A disproportionate amount of people play the winner’s game and believe they can rule out VT.
Ruling out VT is a winner’s game and should only be done by the highly skilled (i.e., cardiologists and probably only when following an electrophysiology study in stable patients). If you are not sure how the Dunning-Kruger effect presents in ECG interpretation, you should not be ruling-out VT.
When an ECG demonstrating a WCT is posted online a surprising amount of EMS providers default to calling it SVT with aberrancy or hyperkalemia, or even more puzzling, SVT with a bundle branch block and hyperkalemia. Many reasons why a given ECG cannot be VT will be posted, and most of them are simply incorrect. There are no ECG features that rule out VT, but many features of an ECG that help to rule in VT. Some ECGs simply cannot be differentiated past the point of being a WCT without the patient being sent for an electrophysiology study.
There is a disproportionate occurrence of EMS providers ascribing hyperkalemia to any ECG. Even when there is a history that strongly points away from hyperkalemia. I refuse to believe in the epidemic of cryptic idiopathic hyperkalemia striking our nation. If I could be so bold as to state what I feel should become two eponymous rules of ECGs being posted on the internet, I present Behn’s rules.
Behn’s rule 1(pronounced Bean’s rule): as an online discussion about a given ECG grows longer, the probability of someone calling any ECG hyperkalemia, regardless of the findings on the ECG or patient the patient’s history, approaches 1.
Behn's rule 2: No matter how obvious the MI is on the ECG is, when posted on line, as the discussion grows longer, the probability of someone saying they would do a right-sided or posterior ECG, or both, approaches 1.
If you can’t help it: If you cannot just look at an ECG with a WCT and call it a WCT and move on from there, here is a proposed framework for differentiating SVT from VT. Approach an ECG with a WCT and have a mental model of the VT-SVT probability gauge in your head. Begin by assigning them a rough probability of VT based on the following: Are they under 18? It is more likely to be SVT than VT. Are they between 18 and 35? It could be either. Are they over 35? It is more likely to be VT. Are they over 60 and have a cardiac history? It is likely to be VT. None of these are absolutes and none of these really matter anyway.
For example, in the graphic below I assigned the rough pre-test probability to three fictitious patients based on nothing more than my best guess. The patient on the left is older and has a cardiac history, I’d have to work really hard, harder than I am willing to work, in order to disprove a WCT from being VT. The 41-year-old female with palpitations with a WCT on the ECG could go either way, SVT or VT. The 18-year-old who did too much blow is less likely to have VT when they are in a WCT—but remember that less likely is not the same thing as impossible.
After considering the demographical factors, consider their history. Are they 30 years old but have a complex cardiac history, can tell you who their cardiologist is, and are prescribed amiodarone? If so, you should update your beliefs on how likely this WCT is to be VT. This is establishing a pre-test probability, with a side of Bayesian updating.
Once you have a “best guess” on the likelihood of the patient having VT based on their age, history, and presentation, look for clues on the ECG that will further change your beliefs. Supposing the patient is a 41-year-old female with a chief complaint of palpitations. Without an ECG, upon feeling her weak radial pulse at 190 beats per minute, you place her as 60% likely to be in VT, based on your best guess. When she tells you her history, that she has had 2 previous heart attacks and 3 stents placed you increase your best guess of the chances that this arrhythmia being VT to 70%. After looking at her 12 lead ECG and noticing a fusion beat you are now 90% certain, if not higher, that this is VT.
A field guide to the common myths surrounding VT and the ECG with a wide complex tachycardia
Adenosine: A common myth revolves around the diagnostic powers of adenosine. Many incorrectly believe that if adenosine converts the arrhythmia that it was not VT. Unfortunately, this is not true. Up to 10% percent of ventricular tachycardias respond to adenosine. Adenosine terminates some forms of VT, most often in ventricular outflow tract VT or fascicular VT.
Width: There is no width criteria for VT. A QRS complex cannot be too wide for VT. While a really wide QRS complex should make you consider hyperkalemia, the width does not rule out VT. Hell, the QRS does not even have to be wide to be VT—Fascicular VT is often narrower than the magic QRS width of 0.12 Axis: VT can have any axis it wants. There is no electrical axis that rules out VT. There are axes (this looks weird, but it is the plural of ‘axis’) that make VT more likely, but none that rule out VT. A normal electrical axis does not rule out VT. Concordance: If it is present in the precordial leads, it makes it more likely to be VT, but the absence of concordance does not rule out VT. And just to throw another wrench in things, you can have concordance in the precordial leads with SVT with aberrancy.
(see figure 4 here - Wide Complex Tachycardias: Understanding this Complex Condition: Part 1) Rate: If it is less than 120 BPM then you may call it AIVR, but other than that, rate does not rule out VT. If the ventricular rate is approaching 300/min it might be worth considering that other rhythms like 1:1 atrial flutter with aberrancy might be more likely. Pulses present: If you are unaware that VT can have a pulse, y’all need an ACLS refresher. Patient stability: VT can be an incidental finding on some people when they get a routine examination at a doctor’s office. Patients with VT can be extremely stable and complaint-free. Ruling out VT based on a patient’s presentation is faulty logic.
The only finding on an ECG that I believe is truly meaningful with a regular WCT is the presence of dissociated P waves or the presence of fusion beats; both findings strongly favor a diagnosis of VT. There are other algorithms that are both sensitive and specific, but they must be employed by experts and used frequently to ensure competency—plus they really don’t change the treatment anyway.
The loser’s game approach to wide complex tachycardia:
1. If they are unstable, cardiovert them. 2. If they are stable, look for evidence of atrial/ventricular dissociation. If dissociated P waves are present or fusion beats are present this is probably VT. If no A/V dissociation is present, go to step 3. 3. Intently stare at the ECG, while ignoring your patient and everyone on the scene. Mumble to yourself incomprehensibly. Try to remember any criteria for VT versus SVT. Maybe look something up on your phone for a minute? If you use Vereckei’s criteria, realize the ER will not know what you are talking about, and you’ll realize you’re not really sure how to pronounce Vereckei anyway. Mentioning of Josephson’s sign will elicit blank stares from the ER staff. Also know this, that no matter what you call the rhythm on the ECG, the ER staff will disagree with you; if you call it VT, they will call it SVT with aberrancy, if you call it SVT with aberrancy, they will call it VT. There is no winning this situation. Go to step 4. 4. Stop screwing around and call it a wide complex tachycardia. If there is a fixable cause (such as a TCA OD or cocaine or hyperkalemia, etc. BASED ON THE HISTORY) then you should fix that. Otherwise, you should do the ACLS things from ACLS class like adenosine and amiodarone or sedation and synchronized cardioversion. If you have been in EMS for more than 20 years and are working with a newer partner tell them about how you used to have a Plano tackle box full of bretylium and isoproterenol.
In Defense of ECG Nerdism.
Please do not equate the above article as defending a sort of dumbing down of cardiology. Make no mistakes here, this is not saying “treat the patient, not the monitor.” We should use a rational approach to thinking, only investing time and energy into things that make a difference. There are times to scrutinize an ECG and to know the subtleties of certain findings. ECG findings such as Wellen’s syndrome, DeWinter’s T waves, and the Sgarbossa criteria can have meaningful impacts on patient outcomes. Understanding the findings of occlusion myocardial infarctions that do not meet STEMI criteria can improve patient outcomes and save lives. Spend your time wisely. Focus on things that matter.
- Brian Behn
Thanks to AM and JB for giving this a once over.