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MY Comment by KEN GRAUER, MD (10/17/2020):
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Today’s patient is a 70-something year old woman who presented to the ED for possible acute Covid-19 symptoms. She was conscious, but appeared acutely ill at the time the initial ECG was obtained in the ED (Figure-1). The computer interpretation read, “Extreme wide complex tachycardia”.
- How would YOU interpret the cardiac rhythm in ECG #1?
- Should you treat with Adenosine? Amiodarone? Immediate cardioversion? — or — Would you first do something else?
MY Thoughts on ECG #1: At 1st glance — ECG #1 indeed appears to be an “extremely wide tachycardia” in this acutely ill, elderly patient. That said — there are 2 things that “don’t fit”. These are:
- My 1st Concern: The rate of the ventricular response is extremely rapid = about 260/minute. While clearly not impossible for VT to be this fast — it is not common for a patient to remain conscious at this fast of a ventricular rate.
- My 2nd Concern: There appear to be some narrow QRS complexes occurring at a fairly regular rate in at least some of the leads in ECG #1 (See BLUE arrows in Figure-2).
PEARL #1: I’ve emphasized on a number of occasions in Dr. Smith’s ECG Blog how helpful accurate estimation of heart rate can sometimes be. While there are always exceptions — certain cardiac rhythms commonly manifest an atrial or ventricular rate within a general rate range (ie, the atrial rate of untreated atrial flutter in an adult is most commonly between a range of 250-350/minute).
- When the atrial or ventricular rate is rapid and regular — it is far more accurate to estimate the rate by looking at every 2nd or every 3rd complex (or in today’s case — looking at every 5th ventricular complex) — instead of trying to estimate rate by only looking at the R-R interval for a single beat.
- To do this — I first select a part of the QRS complex that occurs precisely on a heavy ECG grid line (See the 1st vertical RED line in the long lead II rhythm strip in Figure-2).
- The RED numbers show that the amount of time it takes to record 5 ventricular beats is just under 6 large boxes (BLUE numbers in Figure-2).
- This means that 1/5th of the rate will be a little bit faster than 300 ÷ 6 — or ~52/minute X 5 ~260/minute. Precise estimation of the ventricular rate is helpful here — since a slightly slower ventricular rate (ie, 220-230/minute) would not be nearly as unusual in a patient with VT who was still conscious.
PEARL #2: The BEST way to establish (and confirm) a diagnosis of Artifact — is to be able to identify an underlying rhythm that “marches through” the artifact.
- In today’s case — even more important than the very rapid rate of the wide complexes — is the strong suggestion (by the BLUE arrows in Figure-2) that an underlying narrow-QRS complex rhythm is present!
Returning to the QUESTIONS that I initially Asked: In answer to the question of whether to give adenosine, amiodarone, or initiate synchronized shock — Recognition of a potential underlying narrow-QRS rhythm (BLUE arrows in Figure-2) should prompt you to immediately GO to the BEDSIDE and LOOK at the PATIENT!
- IF the cause of the wide deflections is artifact — a quick LOOK at the patient will often immediately suggest the cause! In today’s case — this acutely ill patient was having febrile rigors that caused uncontrollable body shaking.
AFTER Body Tremors Resolved: I found this patient’s follow-up ECG, obtained after her tremors resolved to be especially insightful (Figure-3).
- ECG #2 — shows almost complete resolution of the artifact seen in ECG #1. There is now sinus tachycardia with a narrow QRS complex and nonspecific ST-T wave changes, that considering the history — most probably were related to the patient’s underlying non-cardiac medical illness.
Some FINAL Points about ECG #1: 100% confirmation that the wide complexes initially seen in ECG #1 were the result of artifact is forthcoming from several observations:
- RED vertical lines in ECG #1 of Figure-3 show precisely regular occurrence of narrow QRS complexes (seen within the RED ovals in each of the chest leads).
- Using calipers, and looking leftward (ie, earlier) on ECG #1 — Even though we do not see any underlying narrow QRS complex simultaneous with the PURPLE vertical line — we do see a small amplitude, completely on-time narrow QRS complex within the BLUE ovals in leads aVR, aVL and aVF.
- Compare the narrow QRS complexes within the 9 OVALS in ECG #1 — with corresponding QRS morphology in these same 9 leads in ECG #2 after resolution of the artifact. QRS morphology of each of these beats is virtually the SAME! The underlying, narrow QRS complexes (within the 9 colored OVALS in ECG #1) — were simply “hidden” by the huge amplitude artifactual deflections resulting from this patient’s vigorous body rigors at the time ECG #1 was recorded.
PEARL #3: In WHICH extremity were body rigors the most intense at the time ECG #1 was obtained?
- In My Comment, at the bottom of the page in the September 27, 2019 post in Dr. Smith’s ECG Blog — I posted the 3-page article by Rowlands & Moore, which is the BEST description I’ve seen for how to quickly determine WHICH extremity is the source of artifact. Full discussion for my rationale employed in the next few bullets below appears in this article by Rowlands & Moore.
- For clarity — I’ve outlined in GREEN the artifactual deflections in 11 of the leads in ECG #1 of Figure-3. Note that the amplitude of the artifactual deflections is equally large in leads II and III. In contrast — artifact is largely absent in lead I (with the exception of some low-amplitude baseline undulations). This localizes the source of artifact to the Left Foot ( = the one limb that is not involved in the derivation of lead I appearance).
- That the Left Foot is the “culprit” extremity — is confirmed by recognizing that artifactual deflections in the 3 augmented leads are greatest in augmented lead aVF (Note the amplitude of artifact in lead aVF is approximately equal to the amplitude of artifact in limb leads II and III).
- The amplitude of the artifact in the other 2 augmented leads ( = leads aVR and aVL) — is approximately half the amplitude of the artifact in lead aVF (which is as expected according to the formulas provided in the Rowlands & Moore article).
- And finally — the amplitude of the artifact in the 6 chest leads is approximately 1/3 of the amplitude of the artifact in lead aVF (which is also as expected by the Rowlands & Moore formulas, since electrical potential in each of the 6 unipolar chest leads is derived by subtracting the potential of the “indifferent” connection [which is determined after dividing the sum of the limb lead potentials by 3]).
HOW TO Do This QUICKLY: I fully acknowledge the challenge of trying to remember the formulas put forth by Rowlands & Moore. You do not have to!
- The EASY way to recognize the “culprit extremity” in less than 5 seconds — is to see IF there is an approximately equal amplitude for artifact in 2 of the 3 limb leads (with no more than minimal artifact in the remaining limb lead) — and then to look at which of the augmented leads has the greatest amount of artifact. Since lead aVF in today’s case clearly has the largest amplitude of artifact among the 3 augmented leads — the Left Foot is the “culprit” extremity (which makes sense — because the left foot is not involved in the recording of lead I, which is the one limb lead that doesn't show significant artifactual deflection).
- NOTE: There will not always be a single “culprit extremity” cause for artifact — but when there is, and you note the geometrical relationships described above — you have confirmed artifact as the cause, because nothing else shows these mathematical relationships.
REFERENCE: For those interested in More on Recognition of ECG Artifact:
- The September 27, 2019 post — for the Rowlands & Moore article with the above-noted formulas for recognizing the “culprit” extremity.
- The January 30, 2018 post — for arterial pulsation artifact.
- Brief review by Tom Bouthillet on some common causes of artifact.
- VT Artifact — by Knight et al: NEJM 341:1270-1274, 1999.
- Artifact simulating VFib — CLICK HERE.
- More VT-VFib artifact — CLICK HERE.
- Artifact simulating AFlutter — CLICK HERE.
- Parkinsonian Tremor vs AFlutter — CLICK HERE.
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APPRECIATION: My sincere THANKS to Prateek Sehgal (Toronto, Canada) for sharing the tracings and this case with us!
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