Friday, January 26, 2024

WillyF- DRAFT- Dyspnea, Older Woman- OMI? (1-26.1-2024)-I_AM_DONE


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MY Comment, by KEN GRAUER, MD (1/27/2024): 

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Today's patient is a woman in her 90s with a dual-chamber pacemaker — who presents with acute dyspnea. I focus My Comment on a few additional thoughts to Dr. Frick's excellent discussion regarding ECG findings in today's initial ECG (that I have reproduced in Figure-1).
  • Being told that today's patient has a permanent pacemaker is extremely helpful in keying us in to the need to look especially close for pacemaker spikes (that had we not been told the patient had a pacemaker — might be extremely easy to overlook).
  • As I discussed in detail in My Comment at the bottom of the page in the January 13, 2024 post in Dr. Smith's ECG Blog — pacemaker spikes tend to be a high frequency signal. As a result — they are often effectively filtered out by a monitor mode setting of 0.5-to-40 Hz. If this is the filter setting used — then pacer spikes may simply not be visible on ECG. 
  • Instead — a broader passband (typically from 0.05 Hz to 150 Hz) is recommended for diagnostic mode, for which emphasis is on optimally accurate ST segment analysis (and for a much better chance of seeing pacemaker spikes on ECG). We were not told the frequencies used in today's ECGs.
  • As per Dr. Frick — pacemaker spikes are best seen in lead aVL of ECG #1. Knowing this relative location of pacemaker spikes in lead aVL with respect to the QRS complex in this lead facilitates recognizing the even smaller pacemaker spikes present in a number of other leads (within the GREEN circles in Figure-1).


Recognition of PTA (Pulse-Tap Artifact):
Dr. Frick highlights a number of essential points for recognizing PTA. These include:
  • Realization that artifact often produces bizarre ST-T wave morphology.
  • Awareness that one of the 3 standard limb leads is often "spared" from this bizarre ST-T wave morphology (which is lead II in Figure-1).
  • Remembering to look at the patient for a potential cause of artifact (which was the presence of the patient's dialysis AV fistula in her left arm in today's case).
  • Repeating the ECG after repositioning and verifying correct electrode lead placement.

Figure-1: I've labeled the artifact in today's initial ECG.


Finding the "Culprit" Extremity: 
As per Dr. Frick — the "culprit" extremity in today's case is the LA electrode. As I review in the August 26, 2022 post of Dr. Smith's ECG Blog — when the cause of artifact is attributable to a single extremity, it is EASY to quickly determine the "culprit" extremity:
  • A single extremity is suggested as the cause of artifact when the amount of artifactual ST segment deviation is approximately equal in 2 of the 3 standard limb leads (ie, outlined in RED in leads I and III of ECG #1) — and essentially not seen in the 3rd standard limb lead (ie, there is minimal ST segment deviation in lead II of ECG #1).

  • By Einthoven's Triangle (See Figure-2) — the finding of equal ST segment amplitude artifact in Lead I and Lead III, localizes the "culprit" extremity to the LA ( = Left Arm) electrode.
  • The absence of ST elevation or depression in lead II is consistent with this — because, derivation of the standard bipolar limb lead II is determined by the electrical difference between the RA and LL electrodes, which will not be affected if the source of the artifact is the left arm (as in Figure-2).

  • By Einthoven's Triangle — the finding of maximal amplitude artifact in unipolar lead aVL confirms that the left arm is the "culprit" extremity (highlighted in RED in lead aVL of ECG #1).
  • By the electrophysiologic principles of Rowlands & Moore (J Electrocardiology 40:475, 2007) — the amplitude of the artifact in the other 2 augmented leads (ie, leads aVR and aVF) — is about 1/2 the amplitude of the artifact in lead aVL (BLUE outline of the depressed ST segments in leads aVR and aVF of ECG #1).
= = = = = = = = = = = = = = = = = = = = =  
  • KEY Take-Home POINT: When the cause of artifact originates from a single extremity — the relative amount of artifact will be maximal in 2 of the 3 standard limb leads — absent in the 3rd standard limb lead — and maximal in the unipolar augmented electrode of the "culprit" extremity (which as per the RED outline in Figure-1 — is lead aVL). Appreciation of these electrophysiologic principles allowed me to instantly identify lead aVL as the "culprit" extremity in today's case — because this is the augmented lead with maximal artifact!
= = = = = = = = = = = = = = = = = = = = = 
Figure-2: Use of Einthoven's Triangle to determine the electrical voltages in the 3 standard limb leads.



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Links to Examples of ARTIFACT:
What follows below is an expanding list of technical "misadventures" — most from Dr. Smith's ECG Blog — some from other sources (NOTE: As I did not previously keep track of these — there are additional examples of artifact sprinkled through Dr. Smith's ECG Blog that I have not yet included here ... ).




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For a "study" in artifact — Check out the January 15, 2024 post in Dr. Smith's ECG Blog, of the case by Drs. Jenkins and Frick (with My Comment at the bottom of the page).



Jan. 15, 2024

https://hqmeded-ecg.blogspot.com/2024/01/noisy-low-amplitude-ecg-in-patient-with.html



ADD LINK to January 13, 2024 post - My Comment Filters, re Pacing!

Attention to filter settings when looking for pacing spikes!

https://hqmeded-ecg.blogspot.com/2024/01/orthostatic-hypotension-onset-after.html



ME TO ADD FIGURE OF EINTHOVEN's TRIANGLE — to localize the lead !!!!! 




QUESTION:

  • XXXX




MY Thoughts on Today's CASE:
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  • XXXXX




January 17, 2023
https://hqmeded-ecg.blogspot.com/2023/01/a-60-year-old-with-chest-pain.html

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My Comment by KEN GRAUER, MD (1/17/2023):
https://hqmeded-ecg.blogspot.com/2023/01/a-60-year-old-with-chest-pain.html
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As per Dr. Smith — pulse-tap artifact used to be a "new" phenomenon to us (as well as to virtually all medical providers). This is no longer the case!
  • In the December 5, 2022 post of Dr. Smith's ECG Blog — We show 4 additional cases of this pulse-tap artifact. There are many more cases — reflecting the interesting phenomenon in medicine when we find ourselves going for years without awareness of a particular entity — until it is brought to our attention. Thereafter, we find ourselves seeing this entity all the time — finally realizing that the entity probably had always been there, but went undetected by us because we simply did not yet know the entity existed ...

  • I reference below to LINKS from a number of additional cases of various artifacts that I've encountered. The BEST way to get good at recognizing artifact — is to be aware of how amazingly common artifact is in practice — to lower your threshold when a tracing for whatever reason "looks weird" — to return to the bedside and LOOK at the patient (scratching, shivering, tremor, etc. make for wonderful sources of artifact) — to reposition the leads (sometimes best if YOU do this yourself!) — and to promptly repeat the ECG. You'll be surprised at how often those "weird deflections" magically disappear!

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NOTE: The reasons I especially liked today's case are: i) The patient presented with chest pain — so the importance of distinguishing artifact from reality can not be overstated! — ii) Artifactual deflections in today's case are rounded, therefore not as obviously distorted as in many cases of artifact (ie, easier to overlook!); — iii) The repeat tracing in this patient with chest pain was not "normal" — although it was nevertheless obvious on repeating the ECG that the most marked deflections had "magically" disappeared after repositioning the left leg electrode; — and, iv) Today's tracing also shows a bizarre "bigeminal" form of artifact that I have not seen before!
  • For clarity in Figure-1 — I've labeled today's initial tracing, and have put it together with the repeat ECG.
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QUESTIONS:
  • Do you know why the largest artifactual deflections in ECG #1 are RED? Why are the smallest artifactual deflections GREEN?

  • HINT: In My Comment at the bottom of the page in the August 26, 2022 post in Dr. Smith's ECG Blog — I work through via application of Einthoven's Triangle, the physiologic rationale for the relative size of artifactual deflections (depending on where the "culprit extremity" is).

Figure-1: Comparison between the initial ECG — and the repeat ECG in today's case after repositioning the LL ( = Left Leg) electrode. (To improve visualization — I've digitized the original ECG using PMcardio).


My Thoughts on ECG #1:
The rhythm in ECG #1 is sinus — with clearly upright sinus P waves with fixed PR interval preceding each QRS in the long lead II rhythm strip.
  • Did YOU Notice the change in both the baseline — as well as in the size of the ST-T wave alternating every-other-beat in the long lead II rhythm strip?

KEY Point: As emphasized by Samaniego et al (Emerg Med J 20: 356-357, 2003) — there are 2 main sources of artifact — which are "physiologic" vs "non-physiologic" sources:
  • Non-Physiologic Artifact Sources — include 60 hertz cycle interference (from AC current devices in the area) — and/or cable or electrode malfunction (ie, loose or broken wire, loose electrode lead connection, etc.).
  • Physiologic Artifact Sources — include patient movement and/or voluntary or involuntary muscular activity (ie, tremor, shivering, scratching, coughing, hiccups, distressed breathing, etc.).

  • Bottom Line: I simply did not know how to explain WHY any of the above physiologic sources of artifact would result in such perfect alternation of the ECG baseline and artifactual distortion of the ST-T wave for all even-numbered beats in ECG #1, but not for the odd-numbered beats!


What is the "Culprit" Extremity in ECG #1? 
As per Dr. Smith — the "culprit" extremity in today's case is the LL electrode. As I review in the August 26, 2022 post of Dr. Smith's ECG Blog — when the cause of artifact is attributable to a single extremity, it is EASY to quickly determine the "culprit" extremity:
  • A single extremity is suggested as the cause of artifact when the amount of artifactual ST segment deviation is approximately equal in 2 of the 3 standard limb leads (ie, outlined in RED in leads II and III of ECG #1) — and not seen at all in the 3rd standard limb lead (ie, the ST segment is neither elevated nor depressed in lead I of ECG #1).

  • By Einthoven's Triangle (See Figure-2) — the finding of equal ST segment amplitude artifact in Lead II and Lead III, localizes the "culprit" extremity to the LL ( = Left Leg) electrode.
  • The absence of ST elevation or depression in lead I is consistent with this — because, derivation of the standard bipolar limb lead I is determined by the electrical difference between the RA and LA electrodes, which will not be affected if the source of the artifact is the left leg.

  • By Einthoven's Triangle — the finding of maximal amplitude artifact in unipolar lead aVF confirms that the left leg is the "culprit" extremity (highlighted in RED in lead aVF of ECG #1).

Finally, as I discuss in My Comment in the August 26, 2022 post (which applies the electrophysiologic principles of Rowlands & Moore: J. Electrocardiology 40:475,477, 2007):
  • The amplitude of the artifact from a single extremity source, is maximal in the unipolar augmented electrode of the "culprit" extremity (which as per the RED outline in Figure-1 — is lead aVF).
  • The amplitude of the artifact in the other 2 augmented leds (ie, leads aVR and aVL) — is about 1/2 the amplitude of the artifact in lead aVF (BLUE outline of the elevated ST segments in leads aVR and aVL of ECG #1).
  • The amplitude of the artifact deflections in the 6 unipolar chest leads is even more reduced (to ~1/3 the size of the artifact in leads II,III,aVF — as suggested by the GREEN outline of the curved ST segment elevations in each of the 6 chest leads in ECG #1).

  • PEARL: Nothing else shows a fixed relation to the QRS complex in the mathematical relationships described above — in which there is equal maximal artifact deflection in 2 of the 3 limb leads (with no ST segment deviation in the 3rd limb lead) — in which maximal artifact in the unipolar augmented lead will be seen in the extremity electrode that shares the 2 limb leads that show maximal artifact (as according to Einthoven's Triangle).

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


Today's Case CONCLUSION:
Take another LOOK at Figure-1. It was after Dr. Smith suggested repeating the initial ECG after repositioning the LL electrode — that ECG #2 was recorded.
  • In your mind's eye — Wouldn't ECG #1 look like ECG #2 if we took away the artifactual deflections highlighted in RED, BLUE and GREEN?
  • That said — there is nonspecific ST-T wave flattening in multiple leads of ECG #2, as well as T wave inversion in lead V2. There are also fairly large U waves in leads V3 and V4. Finally — significant baseline artifact persists in leads II and III of ECG #2, suggesting there may still be some patient movement localized to the left leg.

  • MY Impression of ECG #2: Keeping in mind that the patient in today's case presented with chest pain — the nonspecific ST-T wave flattening in multiple leads, with T wave inversion in lead V2 could be ischemic — albeit clearly not suggestive of an acute event! Serum K+/Mg++ levels need to be checked — as hypokalemia/hypomagnesemia are common causes of nonspecific ST-T wave flattening with U waves.

  • Finally — Did YOU Notice that there is no longer alternate beat variation in the long lead II baseline, nor in ST-T wave morphology. MY Theory: Given that we know the source of ST-T wave artifact in ECG #1 arises from the LL extremity — I suspect the type of patient movement causing this artifact was such that LL electrode skin contact was compromised every-other-beat. Repositioning the LL electrode must have resolved this problem.

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Willy Frick-DRAFT-BLANK- XXX (1-26.1-2024)-BLANK DRAFT

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Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio).



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Willy Smith DRAFT as of 1-26.1-2024:
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 Written by Willy Frick

A woman in her 90s with a history of end stage renal disease and complete heart block status post dual chamber pacemaker presented from home with acute onset dyspnea. ECG is shown below.

What do you think?


The ST and T wave abnormalities jump off the page, but let's set that aside just for a moment to review the tracing systematically. The rate is 60 (and remember, slower heart rates are often seen in OMI). Close inspection reveals pacing spikes, best seen in aVL, so there is ventricular paced rhythm. Many ECG readers will not comment any further on rhythm once ventricular pacing has been identified, but it is still critical to determine the atrial rhythm. In this case, it is atrial fibrillation. This could be easily overlooked since there is complete heart block, but recognizing the atrial arrhythmia likely means prescribing anticoagulation to prevent stroke.

Given that this is a ventricular paced rhythm, we judge the presence or absence of OMI using Smith Modified Sgarbossa Criteria. It is hard to identify exactly how deep the S waves in I and aVL are, but there could be disproportionate ST elevation and hyperacute T waves with reciprocal changes in III and aVF, altogether concerning for high lateral OMI.

The ER immediately contacted cardiology for consideration of emergent catheterization. Cardiology felt that there was baseline artifact and recommended immediate repeat ECG which is shown below.


This ECG actually has even more baseline wander than the first. In addition to having a particularly bizarre T wave morphology, it is curious that among the limb leads, lead II seems to look relatively normal, just as it did in the first ECG. What could explain this very bizarre looking ST-T morphology which completely spares lead II?

Arterial pulse tapping artifact!

The vector mathematics are explained in detail in the above post, but the important point for localization is recognition that lead II is spared. Lead II connects the R arm and L leg, therefore by process of elimination, the problem is with the L arm electrode. (Remember that the R leg is the ground electrode.) On exam, the L arm electrode was overlying the patient's AV fistula. After repositioning the electrode, repeat ECG was obtained showing resolution of the artifact.


Learning points:
  • Arterial pulse tapping artifact causes bizarre ST-T morphology
  • It also characteristically spares exactly one of the limb leads, and the spared lead tells you which electrode is causing the artifact
  • Repeat ECG will reproduce the artifact if the electrodes are not repositioned
  • Ventricular paced rhythm is an incomplete rhythm analysis, you must also determine the atrial rhythm


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