Monday, December 5, 2022

Are these Hyperacute T-waves?

I received this ECG in a text message, with the message:

"Hey, these look like hyperacute T waves to me, what do you think?  It’s an intubated septic nursing home patient."  

"Here is her old ECG:"

What do you think?

Here is my response:

"There is something wrong with this ECG.  It might be another case of pulse tapping artifact. Change the location of the limb Electrodes and repeat the EKG.  All leads except lead I look bizarre."

So he repeated the ECG after moving the limb lead electrodes:

Much less bizarre appearing, and without the suggestion of hyperacute T-waves

Pulse Tapping Artifact

Ever since learning about "Pulse Tapping Artifact," I have begun seeing it more.   It may be that it is much more common than we think but just not recognized.

We have posted Pulse Tapping Artifact 3 times before:

I was shown this ECG without any information. What do you think?


All leads are derived from 3 bipolar electrodes and one unipolar electrode.
Leads I, II, and III depend on bipolar leads voltage differences:
--Lead I uses the right and left arm
--Lead II uses the right arm and the leg
--Lead III uses the left arm and the leg.
--The Wilson (or Goldberger) Central Terminal is used to produce the augmented (a) leads:
aVR, aVL, aVF.

The voltages are calculated as follows (Thanks to Ken Grauer for sending these):
  • I = L - R
  • II = F - R
  • III = F - L
  • aVR = R - (L + F/2)
  • aVL = L - (R + F/2)
  • aVF = F - (R + L/2)
As you can see, the only lead that does not use the left arm electrode is lead II.  Since lead II is the only normal lead in this ECG, the left arm electrode must be the affected electrode.  Indeed, the patients dialysis fistula was on the left arm and was pulsating with each heart beat, moving the electrode and causing artifact.

Arterial pulse tapping artifact

This online article references the article below by Emre Aslanger, a great guy who occasionally corresponds with me about ECGs.

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.

Incredibly, this case was just 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:

It is full text!! 

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.”

Comment by KEN GRAUER, MD (12/5/2022):
I'll start with My Confession: I looked at today's tracing too fast ...
  • I didn’t know the history.
  • I thought the dramatic increase in chest lead amplitudes (ie, very deep S waves in anterior leads — with very tall R waves in V5,V6) — together with tall, peaked anterior T waves — and QTc prolongation with deep symmetric T wave inversion in V5,V6 — could all be explained by marked LVH with LV “strain” and/or ischemia. I thought the overall picture in these 6 chest leads did not look like acute OMI.

I was admittedly stumped by the limb leads:
  • As per Dr. Smith — the limb lead appearance is bizarre. That said — given what I had convinced myself could be a plausible chest lead picture of marked LVH with QTc prolongation — I thought that IF the limb lead appearance was “real” — then the combination markedly peaked inferior lead T waves + reciprocal T wave inversion in lead aVL + extreme QTc prolongation — might reflect Takotsubo Cardiomyopathy. 

PEARLS for Recognizing Pulse-Tap Artifact:
As per Dr. Smith: Now that we know about Pulse-Tap Artifact — We seem to be recognizing it more and more.
  • If ever you see a bizarre appearance for 2 of the 3 standard limb leads (ie, leads I,II,III) — with the 3rd standard limb lead looking relatively (if not completely) appropriate — Think Artifact! This is precisely what we see for the initial ECG in today's case ( = ECG #1 in Figure-1) — in which the huge and bizarrely pointed T waves in lead II and lead III are distinctly out of character compared to the unremarkable flattened ST segment with shallow T wave inversion in lead I.

  • Since the cause of the Pulse-Tap Artifact is contact of one of the limb lead electrodes with a pulsating artery below it — the bizarre deflection that you suspect is artifact will have a fixed relationship to neighboring QRS complexes. This is precisely what we see for ECG #1 — in that the coupling distance from the QRS until the peak of the T wave in leads II and III remains constant for each beat (best seen for each beat in the long lead II rhythm strip at the bottom of the 12-lead).

  • KEY POINT: You can confidently make the diagnosis of Pulse-Tap Artifact by seeing IF the geometric relationships predicted by Einthoven’s Triangle regarding the relative size of artifact deflections holds true. I illustrate this concept in Figure-1 — in which the RED outlines in ECG #1 show the relative size and shape of the "extra deflection" added on by the pulse-tap artifact to the ST-T wave in the various leads.
  • According to the 3-page article by Rowlands and Moore (J Electrocardiology 40: 475-477, 2007 — which I reproduce in the ADDENDUM below) — the amplitude of the artifact is maximal in the unipolar augmented electrode of the "culprit" extremity, which is lead aVF in ECG #1. The amplitude of the artifact in the other 2 augmented leads (ie, leads aVR and aVL) will be about 1/2 the amplitude of the artifact in lead aVF.
  • That maximal augmented lead artifact is seen in lead aVF — is consistent with the finding in ECG #1 of comparable artifact amplitude in leads II and III — but essentially no artifact in standard lead I. This is because electrical potential from the left leg electrode (ie, aVF) does not influence the QRS complex in lead I (which is derived from the difference in electrical potential between the RA and LA electrodes, without contribution from the LL electrode — as seen in Figure-2 in the ADDENDUM below).
  • Rowlands and Moore go on to emphasize that the amplitude of artifact deflections in the unipolar chest leads (based on the equation cited in the top-right column of page 477) — should be only about 1/3 the size of the maximal artifact distortion that is seen in leads II, III and aVF. This too is consistent with the relative size of the artifact in ECG #1.

  • Finally: You can prove the “culprit extremity” cause of artifact by demonstrating that artifact deflections are no longer present after repositioning the limb lead electrodes (which is evident in ECG #3). A lesser level of baseline artifact does remain in the limb leads of ECG #3 — but this looks nothing like the bizarrely peaked pulse-tap T waves of ECG #1

Figure-1: Comparison of the initial ECG in today's case — with the repeat ECG obtained after repositioning the limb leads. The RED outlines in ECG #1 show the relative size and shape of the "extra deflection" added on in the various leads by the pulse-tap artifact. BLUE arrows correlate the timing of artifact deflections in various leads. The PURPLE arrow shows the absence of pulse-tap artifact in lead I.



To facilitate visualization of the electrical relationships cited above by Dr. Smith — I've added Figure-2 below. As per Dr. Smith — the fact that the ST-T wave in lead I of ECG #1 does not manifest any artifact distortion rules out the RA (Right Arm) and LA (Left Arm) electrodes — thereby implicating the LL (Left Leg) as the "culprit" extremity producing the artifact.
  • By Einthoven's Triangle — the finding in ECG #1 of maximal amplitude artifact in unipolar lead aVF (compared to the amplitude of artifact in the other 2 augmented leads = aVR and aVL) — confirms that the LL electrode (which is placed on the left foot) is the "culprit" extremity.

Figure-2: Use of Einthoven's Triangle to determine the electrical voltages in the 3 standard limb leads.

NOTE: I reproduce below (in Figures-3, -4 and -5— the 3-page article by Rowlands and Moore (J. Electrocardiology 40: 475-477, 2007) — which is the BEST review I’ve seen on the physiology explaining the relative size of artifact deflections when the cause of the artifact is from a single extremity.

  • As noted by the equations on page 477 in the Rowlands and Moore article: i) The amplitude of the artifact is maximal in the unipolar augmented electrode of the “culprit” extremity — which is lead aVF in ECG #1; andii) The amplitude of the artifact in the other 2 augmented leads (ie, leads aVR and aVL) is about 1/2 the amplitude of the artifact in lead aVF. These relative artifact sizes are consistent with the amplitudes of ST-T wave distortion seen in ECG #1.

  • The amplitude of artifact deflections in the unipolar chest leads (based on the equation cited in the top-right column of page 477) — should be only about 1/3 the size of the maximal artifact distortion that is seen in leads II, III and aVF. 


Figure-3: Page 475 from the Rowlands and Moore article that I reference above.


Figure-4: Page 476 from the Rowlands and Moore article that I reference above.


Figure-5: Page 477 from the Rowlands and Moore article that I reference above.

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