Friday, March 17, 2023

A woman in her 50s with chest pain and dyspnea

Submitted by anonymous, written by Pendell Meyers

A woman in her 50s presented to the Emergency Department with chest pain and shortness of breath that woke her from sleep, with diaphoresis. She had a prior history of "NSTEMI" one month ago, during which she had a coronary angiogram reportedly showing no stenosis in any coronary artery. Her vitals were within normal limits.

Here is her triage ECG:

PM Cardio Version (see original screenshot I received below)

Original image. What do you think?

Here is the prior ECG on file (from 1 month ago, when she was having "NSTEMI" with high sensitivity troponin peaking at 200 ng/L):

What do you think now that you can see the prior ECG?

These two ECGs were sent to me, with the clinical info above. 

I replied: "Can you go place the leads yourself and make sure they are normal, then repeat the EKG? DDx, is pulse tapping artifact, reperfusion, and takotsubo. Pulse tapping artifact usually goes away with fixing electrode placement problem, and lead I looks so normal that this is probably pulse tapping artifact."

I sent the first ECG with no information at all, and without the old ECG, to Steve Smith who immediately just texted back: "pulse tapping."

Smith: how did I know this instantly?  Because lead I is normal.  All other leads are very weird.  In pulse tapping artifact, one of lead I, II, and III will be normal.

Another ECG was performed immediately with new electrodes and correct placement (no information given about whether there was any obvious misplacement or arterial pulsation source on initial placement):

Serial troponins were undetectable. She was ultimately discharged home after ED workup.

Smith comment: now that I easily recognized pulse tapping artifact, I see it about once a week.  I believe it is far more common that previously recognized.

See these other cases of arterial pulse tapping artifact:

A 60 year old with chest pain

More info on arterial pulse tapping artifact

Aslanger E, Yalin K. Electromechanical association: a subtle electrocardiogram artifact. Journal of Electrocardiology. 2012;45(1):15-17. doi:10.1016/j.jelectrocard.2010.12.162.

This case was published in Circulation on January 22, 2018 (thanks to Brooks Walsh for finding this!) 
Asymptomatic ST-Segment–Elevation ECG in Patient With Kidney Failure.  Circulation. Originally published January 22, 2018

Here is a case from Circulation year 2000 that was misdiagnosed as due to pancreatitis.  But you can tell from the normal lead III that this was a right arm electrode problem:

Why is there also artifact in precordial leads?

Aslanger explains:
“[O]ne may expect that the leads not connected to the electrode affected by the source of disturbance would be free of distortion; but this is not the case. When one of the limb electrodes is affected by a source of disturbance, it distorts not only the corresponding derivation but also [the others] which are all calculated by mathematical equations…”
“…precordial leads [are also affected] because the Wilson central terminal, which constitutes the negative pole of the unipolar leads, is produced by connecting 3 limb electrodes via a simple, resistive network to give an average potential across the body.”


MY Comment, by KEN GRAUER, MD (3/17/2023):


We continue to periodically show examples of “pulse-tap artifact” — in the hope that this abnormality becomes more readily recognized. Today’s case provides yet one more example.
  • I initially considered Takotsubo cardiomyopathy as the cause of the ECG in today’s case, for this middle-aged woman with new chest pain and dyspnea — because of the diffuse T wave inversion with obvious QTc prolongation. But on 2nd reflection — I do not recall EVER seeing such pronounced “Wellens’-like” biphasic T waves with steep descent in so many leads! 
  • Today’s ECG just looked strange — ergo immediate recognition by Drs. Meyers and Smith of probable“pulse-tap artifact” as the cause.
  • The “GOOD news” — Pluse-tap artifact is EASY to verify. Simply redo the ECG with care at repositioning the 4 extremity leads to ensure they are no longer in contact with a pulsating artery.

A very similar case to the one presented today appears in the January 17, 2023 post of Dr. Smith’s ECG Blog. I explain and illustrate in that case the relative proportions to expect for ECG deflections in each of the 12 leads when there is pulse-tap artifact.

  • The “culprit” extremity is the LLeg in both cases— easily identified because the “funny” ECG deflection in today’s case is largest in leads II,III,aVF — and completely absent in lead I (a direct result of Einhoven’s Triangle).
  • Because of the electrophysiologic principles — the relative amplitude of artifact will be approximately half the maximum amount in the other 2 augmented leads (ie, in leads aVR and aVL) — and approximately 1/3 the amount in the chest leads (all illustrated and explained in My Comment in the Jan. 17, 2023 post). 

KEY Take-Home Point:

When the ECG in front of you looks “funny” — Think of the possibility of artifact sooner rather than later. Repeat the ECG before you consider activating the cath lab.

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