Tuesday, November 8, 2022

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

I was shown this ECG; "Steve, what do you think of this?":

What is going on?

I said: "This is pulse tapping artifact and a long QT"  

Why did I say that?

Whenever you see a very bizarre EKG, you should think about pulse tapping artifact.  This is when one of the limb lead electrodes is placed over an artery, especially when placed over a dialysis fistula.

When you suspect this, your next task is look for the one lead among leads I, II, and III which is NOT bizarre.  

Lead I in this ECG is not bizarre [though it does show a very long QT (or QU)].

Leads I is formed by the right arm and left arm electrode.

Lead II by the right arm and left leg electrode

Lead III by the left arm and left leg electrode

So if lead I is not bizarre (as in this case), then the electrodes that are NOT affected are the right and left arm.

Thus, the left leg electrode is placed over an artery.

"Augmented leads" (aVR, aVL, aVF): these are all dependent on Wilson's Central Terminal, which is the average of leads I, II, and III.

Precordial leads: these use the limb leads for their grounding, so they are all also affected by one limb lead that is aberrant.

Therefore, as many as 11 of the 12 leads can look bizarre.

Solution: repeat the ECG, but move the left leg electrode.

Pulse tapping artifact was not recognized.

The patient had come to the ED for SOB, but without any chest pain.  He has 3 weeks of progressive fatigue and weakness.  He had a 10 pound weight loss.

He was moved to the critical care area due to his EKG.

His potassium returned at 1.3 mEq/L!

10 mEq of KCl was begun intravenous at 35 minutes after the first EKG.

At 44 minutes, another ECG was recorded.  The electrodes from the first ECG had been removed, so electrodes were placed at a different location by accident, not intentionally:

Now it just looks like severe hypokalemia.  There is a "wavy"pattern.  See here for many examples of the "wavy" pattern of hypokalemia.

There is what appears to be a long QT, but is not.  Look at lead V3.  there are 2 waves after the QRS.  The first is the T-wave (without a long QT); the 2nd is a massive U wave from hypokalemia.  If you trace down from this U wave to lead II (across the bottom), you realize that what you thought was a T-wave in lead II is really a U-wave.  The long QT is really a QU. You can find that all the "long QTs" in every lead are really QU-waves.

This is what I say: "When the QT looks impossibly long, it is probably a QU.

Cardiology was consulted for these ECGs and they were worried about the massive ST Depression and ST Elevation.  I ran into the cardiologist in the hallway and told him, "No, this is pulse tapping artifact."  He was very appreciative to learn about this.

The patient did get a "stat" echo:

Previous EF = 54% 2 years prior

--Normal LV cavity size, normal wall thickness and moderate LV systolic dysfunction.

--The estimated left ventricular ejection fraction is 37 %.

--Global hypokinesis with possible regional wall motion abnormality-inferior & inferolateral


Compared to the Echo from 10/2020, there has been a significant interval change:

1. Ejection fraction has worsened

2. Possible inferior and infero-lateral WMA are new

The next AM, the K had come up to 2.3 mEq/L:

It is normalizing

Troponins reached a peak of 42 ng/L (URL = 34 ng/L).  This was not a myocardial infarction of any kind.

Learning Points:

1. When the EKG looks bizarre, think about pulse tapping artifact

2. Recognized the "wavy" pattern of hypokalemia

3. When you think of Pulse Tapping Artifact, look for the one of leads I, II, or III that are NOT bizarre.

4. When the QT looks impossibly long, it is probably a QU.  Look for the U wave and measure the potassium for hypokalemia.

Other cases of Pulse Tapping Artifact:

Acute chest pain and a bizarre ECG

Bizarre (Hyperacute??) T-waves

Don't miss Ken Grauer's excellent observations on "Technical Misadventures" below!!

MY Comment by KEN GRAUER, MD (11/8/2022):
In addition to the astute diagnosis by Dr. Smith of “Pulse-Tapping Artifact” — the first 2 ECGs in today’s case feature a few additional “technical misadventures”. For clarity — I’ve put these 2 ECGs together in Figure-1.
  • CHALLENGE: How many of these “technical misadventures” can you recognize?

Figure-1: The first 2 ECGs in today’s case. In addition to the pulse-tapping artifact — How many additional “technical misadventures” can you recognize?

"Technical Misadventures" in Today's Case:
Dr. Smith highlights in his discussion above how to instantly recognize the pulse-tapping phenomenon. As in the several cases of this phenomenon that he cites from previous posts in Dr. Smith's ECG Blog (ie, from August 26, 2022 and from January 30, 2018) — it is the distribution of the bizarre ST-T wave deflections in the limb leads that precisely follows the location and relative amount of amplitude distortion predicted by Einthoven's Triangle that prompts immediate recognition of this phenomenon.
  • 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 participation of the RA (Right Arm) and LA (Left Arm) in this technical "misadventure" — 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 in the ADDENDUM 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.

  • 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. 

  • NOTE: The fact that the lead V3 recording in ECG #1 is especially bizarre (with the ST-T wave artifact in this lead clearly magnified much more than the expected 1/3 increase from artifact distortion) — suggests more than a simple pulse-tapping phenomenon is operative. I therefore suspect there has been another "technical misadventure" — but, whatever this was — it  has resolved after extremity electrodes were repositioned (ie, the ST-T wave appearance in lead V3 of ECG #2 done 44 minutes later is not nearly as bizarre as it was for this lead in ECG #1!).


Additional "Technical Misadventures" in Today's Case: 
There are a number of additional "technical misadventures" in today's case. These include the following:
  • The V1 and V2 electrode leads are probably placed too high on the chest in both ECG #1 and ECG #2. As we have pointed out on multiple occasions (See My Comment at the bottom of the page in the April 17, 2022 post in Dr. Smith's ECG Blog) — lead V1,V2 malposition is surprisingly common in practice. The possibility of this technical mishap can be easily recognized by the presence of one or more of the following 3 Clues: i) If there is an r' in leads V1 and/or V2); ii) If there is a negative component to the P wave in lead V1 and/or V2; andiii) If the appearance of the QRS complex in leads V1 and V2 looks similar to the QRS in lead aVR.
  • Note in ECG #1 and in ECG #2 — that the rSr' and the small but negative P waves in leads V1,V2 are no longer present in the 3rd ECG of today's case that was done the following morning! This strongly supports my suspicion that the V1 and V2 electrode leads were placed too high on the chest in the first 2 ECGs.

 — Note the artifact that is present in the limb leads of ECG #2. The fact that baseline artifactual undulations are maximal in leads III and aVR — absent in lead III — and present at approximately 1/2 the amplitude of aVR in the other 2 augmented leads ( = aVL and aVF) — localizes the cause this artifact to the Right Arm! 

  • As emphasized in the article by Rowlands and Moore that I have cited — nothing else produces this consistently proportional amount of artifact distortion!

  • P.S.: As opposed to the discrepancy in the relative amount of artifact distortion in lead V3 of ECG #1 — Note in ECG #2 that the fine baseline artifact undulations in the chest leads are consistent with an approximate 1/3 increase in size of the artifact as expected when the cause of artifact is attributable to a single extremity.

  • NOTE: Although we can localize the artifact distortion in ECG #2 to the RA — this is not a pulse-tapping artifact (because there is no bizarre distortion of ST-T waves). Instead — there must be some other cause ongoing in the "culprit" RA extremity to produce the artifact (ie, tremor, loose electrode lead, etc.).


ADDENDUM (11/8/2022):
  • I've reproduced in Figures-3-4 and -5 — the 3-page article by Rowlands and Moore that illustrates the electrical relationships and expected relative sizing of artifactual distortion caused by a single "culprit" extremity.


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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