Saturday, April 26, 2025

ECG Blog #479 — Technical Misadventures to Know!


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INTRO: I have added this Tab on Technical "Misadventures" — to the Menu at the top of every page in this ECG Blog:

— Where to find this LINK in the Top Menu! —


All-too-often lead reversals, unsuspected artifact, and other "technical misadventures" go unrecognized — with resultant erroneous diagnostic and therapeutic implications. 
  • In the hope of facilitating recognition of these cases — I am developing an ongoing listing on this page with LINKS to examples that I’ve published in this ECG Blog, as well as in Dr. Smith’s ECG Blog where I frequently write commentaries.
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Sample CASE #1:
  • What type of "technical misadventure" is present in Figure-1?

Figure-1: How would you interpret this ECG?


QUESTIONS:
  • What is the "culprit artery" in Figure-1?
  •      — What kind of "lead reversal" ? 

This case is from ECG Blog #375. Click this link for full discussion!
  • HINT: This is not a high-lateral infarction ...
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Sample CASE #2:
  • What type of "technical misadventure" is present in Figure-2?

Figure-2: How would you interpret this ECG?

QUESTIONS:
  • Did you recognize the MI in Figure-2?
  •      — What kind of "lead reversal" ? 

This case is from ECG Blog #175. Click this link for full discussion!
  • HINT: There was no infarction — and no lead reversal ...

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Suggestion:
My favorite on-line “Quick GO-TO” reference for the most common types of lead misplacement comes from LITFL ( = Life-In-The-Fast-Lane). I have used the superb web page they post in their web site on this subject for years. It’s EASY to find — Simply put in, “LITFL Lead Reversal” in the Search bar — and the link comes up instantly. 
  • This LITFL web page describes the 7 most common lead reversals. There are other possibilities (ie, in which there may be misplacement of multiple leads) — but these are less common and more difficult to predict.
  • When I suspect a type of lead reversal that I am less familiar with — I simply review those 7 most common types of lead reversal on the LITFL page — and see if any of the ECG examples they provide seems to apply. 

  • PEARL: — I’ve summarized in Figure-3 those tips that have helped me most over the years to rapidly recognize tracings in which lead reversal is likely.

Figure-3: Tips for recognizing lead reversal (See text).



—  —

ECG Media PEARL #72 (5:45 minutes Audio) — Reviews how to suspect Limb Lead Reversal (especially LA-RA lead reversal).


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EXAMPLES of Lead Reversal on Dr. Smith's Blog:
Technical errors featuring a variety of lead reversal placements remain a surprisingly common “mishap” of everyday practice. As a result — I'll continue to periodically publish clinical examples of lead misplacement. For review — GO TO:

Lead Reversals on My ECG Blog:
  • ECG Blog #264 — Review of Limb Lead Reversals (ie, LA-RA lead reversal in a patient with an acute MI). Please also see the 7/29/2024 ADDENDUM to this post for another LA-RA reversal — V1,V2 misplacement — and an almost flat line in lead II).
  • ECG Blog #330 — LA-RA reversal.
  • ECG Blog #375 — LA-LL lead reversal.
  • ECG Blog #396 — Flat line in lead I. 
  • ECG Blog #462 — Leads are "off" (bizarre frontal plane axis).
  • ECG Blog #463 — LA-RA reversal.

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Links to Examples of ARTIFACT:
More technical "misadventures" are referenced here — some from Dr. Smith's ECG Blog — some from My ECG Blog — and some from other sources.
 
 




 



 

Posted by ECG Interpretation at 12:23 AM 0 comments

Saturday, April 19, 2025

ECG Blog #478 — Torsades or Polymorphic VT?


The lead II rhythm strip shown below in Figure-1 was obtained from an older man who was on multiple medications — and, who presented to the hospital with shortness of breath.

QUESTION:
  • The concern regarding this rhythm strip was whether this patient was having intermittent episodes of Torsades de Pointes or of PMVT (PolyMorphic Ventricular Tachycardia)?

Figure-1: Long lead II rhythm strip — obtained from an older man with acute dyspnea.


MY Thoughts on the Rhythm in Figure-1:
As emphasized in ECG Blog #231 — the ECG appearance during an episode of Torsades and PMVT looks the same! The difference diagnostically between these 2 arrhythmias — depends on whether or not the QTc is prolonged prior to the onset of the ventricular tachyarrhythmia.
  • The above said — neither Torsades nor PMVT is present in Figure-1. 


What Do the RED Arrows Show?
The KEY for interpreting today’s rhythm is highlighted by the RED arrows that I have added in Figure-2.
  • QUESTION: What do YOU see in Figure-2?

Figure-2: What do the RED arrows represent? 


ANSWER: 
The RED arrows in Figure-2 — represent normally conducted (ie, narrow) supraventricular complexes. This is easiest to appreciate when we clearly see 2 narrow QRS complexes in a row (ie, for the narrow QRS complexes highlighted by RED arrows #4,5; 7,8; 10,11; 13,14; 16,17;) — and especially toward the end of this rhythm strip, where we see 3 narrow QRS complexes in a row (ie, for the QRS complexes highlighted by RED arrows #19,20,21 and #22,23,24).
  • Now look at RED arrow #2 near the beginning of the tracing. Note that the narrow QRS complex highlighted by this arrow #2 — is immediately preceded by the 1st of a series of very tall, very wide bizarre complexes (A) — and then followed by 5 consecutive bizarre wide complexes (B,C,D,E,F). 
  • The space between each of these 6 wide, bizarre complexes is no more than 1 large box — which means that the rate of these bizarre complexes (A-thru-F) is ~300/minute!
  • Note that the 1st of these wide bizarre complexes occurs immediately before the QRS highlighted by arrow #2 — and that the 2nd of these bizarre complexes occurs immediately after this QRS. This cannot be! If these wide, bizarre complexes were "real" — then A would have prevented this QRS from occurring. Similarly, B could not have occurred, because it is too close to the QRS during the ARP (Absolute Refractory Period). As a result — these wide, bizarre complexes in Figure-2 can not be "real", and must therefore represent Artifact! 

PEARL #1: The BEST way to identify artifact — is when you can see the underlying cardiac rhythm continue unaffected through the artifact! This is precisely the situation in Figure-2.
  • Although some QRS complexes are easier to identify than others — each of the RED arrows in Figure-2 clearly corresponds to an on-time narrow QRS complex.
  • Note that there are 2 PINK arrows in Figure-2. ( = arrows #3 and #12) These correspond to the 2 places where we would expect 2 on-time QRS complexes to occur (ie, It would be extremely unusual for the 22 on-time QRS complexes that we do see in Figure-2 — to suddenly drop 2 beats without altering the underlying regularity of this rhythm).
  • Thus, the underlying rhythm in Figure-2 — appears to represent some type of supraventricular rhythm at a rate of ~140/minute, albeit without clear evidence of atrial activity. (Then again, there appears to be too much disturbance of the baseline by artifact to tell if atrial activity might be present, but hidden).
  • BOTTOM Line: The presence of an apparent regular supraventricular rhythm throughout the lead II rhythm strip in Figure-2 (albeit with the exception of the 2 PINK arrows) — tells us that these wide, bizarre complexes which manifest an unpredictable variation in morphology, are almost certain to represent artifact.

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The CASE Continues:
In Figure-3 — we see the 12 lead ECG that was recorded simultaneousy with the long lead II rhythm strip seen in Figure-2.

QUESTION:
  • Does this 12-lead ECG in Figure-3 clarify our impression of the long lead II rhythm strip?

Figure-3: The 12-lead ECG recorded simultaneously with today’s long lead II rhythm strip. (To improve visualization — I've digitized the original ECG using PMcardio).

ANSWER:
The simultaneously recorded 12-lead ECG in Figure-3 — confirms our impression that the very rapid and wide irregular deflections in the long lead II rhythm strip are artifact.
  • Note that some artifact is seen in all leads of this 12-lead tracing. That said — Isn't the relative amount of artifact decidedly less for the 4 leads that appear below the horizontal RED line in Figure-4? 
  • By PEARL #1 — Isn't it now easier to confirm the regular occurrence of an underlying supraventricular rhythm in leads III, aVF, V3 and V6?

Figure-4: Which leads manifest the least artifact?

Return for a moment to Figure-3.
  • Among the 3 standard limb leads (ie, leads I,II,III ) — Isn't the relative amplitude of artifact deflections greatest in leads I and II, compared to lead III?
  • And among the 3 augmented limb leads (ie, leads aVR, aVL, aVF) — Isn't the relative amplitude of artifact deflections greatest in lead aVR?
  • PEARL #2: As discussed in ECG Blog #428 — the quick way to identify which exremity is most responsible for producing artifact when 2 of the standard limb leads manifest similar artifact amplitude (as we see for leads I and II in Figure-3) — is to see which of the augmented leads manifests greatest artifact amplitude. Since this is lead aVR — there is likely to be excessive patient movement of the RA (Right Arm) — which can easily be verified by a quick look at the patient!

PEARL #3: Regarding suspected artifact: Look at the patient — and he/she will usually tell you the cause. In today’s case — We are told that the patient presented with shortness of breath. 
  • A quick look at the patient will probably tell you IF the artifact in Figure-4 is resulting from; i) Shortness of breath — with in addition, excessive movement of the right upper extremity; and/or ii) Some other artifact-producing movement (such as tremor, shivering, seizure activity — and/or loose electrode leads).
  • Hopefully the amount of artifact can at least be reduced once the source of this artifact is found and addressed. At that point — Repeat the ECG in the hope of determining if the rapid supraventricular rhythm (about 140/minute in Figure-4) is sinus tachycardia (that should slow down as the patient’s condition improves) — or some other SVT rhythm (such as AVNRT or atrial tachycardia).

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Beyond-the-Core:
Take a final look at today's artifact from another perspective. 
  • Step Back for a moment — and Look from afar at the long lead II rhythm strip. In Figure-5 — Doesn't it seem like there is a pattern to the baseline variation? 
  • MY Thought: It would be interesting to look at the patient and validate whether the repetitive upward slanting BLUE lines in Figure-5 correspond to a respiratory rate of ~50/minute (ie, each breath occurring in a bit more than 1 second).

Figure-5: Stepping back and looking from afar at the pattern of baseline variation.




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ADDENDUM — Links to Examples of ARTIFACT 
More technical "misadventures" are referenced here — some from this ECG Blog; some from Dr. Smith's ECG Blog — some from other sources.
Posted by ECG Interpretation at 5:20 AM 2 comments

Sunday, April 13, 2025

ECG Blog #477 — Is One or Both 3rd-Degree?


Compare these 2 tracings.
  • Is one or both of them 3rd-Degree (Complete) AV Block?
  • If not — Why not?

Figure-1: Is one or both of these tracings 3rd-Degree?

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Let's look at these rhythms one at a time — starting with Rhythm-B:

Rhythm B (which I have reproduced in Figure-2):
As always — I favor the Ps, Qs, 3R Approach for assessing rhythm disorders, as I find this the most time-efficient way to narrow down my differential diagnosis of arrhythmias (See ECG Blog #185):
  • NOTE #1: Lead MCL-1 is a right-sided monitoring lead (providing a comparable view to what we typically see in right-sided lead V1 on a 12-lead ECG).
  • NOTE #2: It does not matter in what order you assess the Ps,Qs,3Rs. I often vary the sequence I use depending on which parameter is easiest to assess in the tracing I am looking at.
  • NOTE #3: If you have a moment of time (ie, If the patient in front of you is not about to have a cardiac arrest) — then using calipers will save you time (and increase your accuracy) for interpreting challenging rhythms.

Figure-2: This is Tracing-B from today's case.

Applying the Ps, Qs, 3Rs to Rhythm-B:
  • P waves are present. We see lots more P waves than QRS complexes (I've labeled with RED arrows in Figure-3 those P waves that we clearly see).
  • The QRS complex is wide ( = 0.15 second). I find it easiest to measure QRS duration by selecting a complex that either begins or ends on a heavy ECG grid line (In Figure-3 — Beat #1 ends on a heavy grid line).

And — The 3Rs (ie, Is the rhythm Regular? — the Rate? — and are P waves Related to neighboring QRS complexes?):
  • The R-R interval in Figure-2 is Regular — and measures just under 8 large boxes in duration (and 300 ÷ a bit less than 8 = a Rate slightly less than 40/minute).
Are P waves Related to neighboring QRS complexes? 
  • Look at the PR interval in front of each QRS in Figure-3. Doesn't the PR interval continually change?

Figure-3: The QRS in Tracing-B is clearly wide. I've labeled those P waves that we clearly see with RED arrows.

QUESTION:
Is the atrial rhythm in Figure-3 regular?
  • Given the regularity of the RED arrows that we do see in Figure-3 — Wouldn't it make more sense for the rest of the underlying atrial rhythm to be regular, instead of all-of-a-sudden dropping several P waves?

  • PEARL #1: Use calipers to answer the above Question! (See the PINK arrows in Figure-4).

Figure-4: I've added PINK arrows to show where my calipers suggest that on-time P waves are likely to be hiding.

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ANSWER:
Although impossible to prove from the short single-lead tracing we show in Figure-4 — it makes much more sense for the underlying atrial rhythm to be regular (instead of having to postulate sudden and unpredictable onset of some unusual type of intermittent SA block).
  • Setting your calipers to the P-P interval between any 2 consecutive RED arrows in Figure-4 — allows us to predict the probable location of underlying on-time sinus P waves ( = PINK arrows in Figure-4).
  • PEARL #2: As shown in ECG Blog #344 — it is common in patients with 2nd-degree or 3rd-degree AV block to manifest slight variation in the P-P interval of underlying sinus P waves. This slight variation in the rate of sinus P waves is known as "ventriculophasic" sinus arrhythmia — and is easy to account for when postulating the probable location of hidden "on-time" sinus P waves.

Putting It All Together for Tracing-B:
The rhythm in Tracing-B is 3rd-Degree (Complete) AV Block.
  • PEARL #3: Complete (or 3rd-degree) AV block — is said to be present when none of the on-time sinus impulses from above are able to conduct to the ventricles despite having an adequate opportunity to do so.

  • KEY Point: It is this last requirement (ie, the need for "adequate opportunity" to conduct) — that is so commonly overlooked. There may be AV dissociation, with none of the on-time P waves in the small segment of the rhythm you are looking at being able to conduct — but unless the ventricular rate is slow enough (usually less than 55-60/minute) — and, unless the duration of monitoring is long enough — it may be that there has not yet been enough of a monitoring period to demonstrate that the degree of AV block is complete.

I illustrate the above concept in more detail in ECG Blog #191 (in which I also review the 3 types of AV Dissociation, of which AV block is only one of these types). For now, the "Take-Home" Point is that Tracing-B in today's case does show 3rd-Degree (Complete) AV Block. Note the following features of this rhythm in Figure-5:
  • The ventricular rhythm is slow, regular — and with a wide QRS complex.
  • The atrial rhythm is regular (RED arrows — showing no more than slight variation in the R-R interval, consistent with ventriculophasic sinus arrhythmia).
  • There is complete AV dissociation — because none of the on-time sinus P waves are related to neighboring QRS complexes (ie, The PR interval in front of each QRS complex continually changes).
  • More than just AV dissociation, there is complete AV Block — because on-time sinus P waves occur at all points within the R-R interval, and fail to conduct despite having more than adequate opportunity to do so.
  • The level of this AV block is below the AV Node (and therefore arising from the ventricles) — because there is a slow idioventricular escape rate (ie, with QRS widening — and an "escape" rate of just under 40/minute).

Figure-5: Tracing-B shows complete AV block.


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What about Tracing-A in today's case? (reproduced in Figure-6):

Figure-6: This is Tracing-A from today's case. (To improve visualization — I've digitized the original ECG using PMcardio).

My First Impression of Tracing-A:
The 12-lead ECG in Tracing-A is obviously abnormal. The marked T wave inversion in leads V1,V2 is impossible to overlook! 
  • The rhythm is extremely slow. 
  • Looking at just the last 2 beats (that occur in simultaneously-recorded leads V1,V2,V3 — and in V4,V5,V6) — I could not initially tell which beats might be supraventricular (ie, with RBBB conduction in lead V1?) — vs ventricular (producing the wide QS complexes in V4,V5,V6?).
  • NOTE #4: In order to complete my interpretation — I would clearly need to determine which of the 4 beats in this tracing are ventricular vs supraventricular (and whether any of these 4 beats might be conducted?).
  • NOTE #5: As I turned my attention to the rhythm — it was also clear that using calipers would be needed. 

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Applying the Ps, Qs, 3Rs to Rhythm-A:
  • The QRS complex looks to be wide (about 3 little boxes = 0.12 second in duration).
  • As noted — the Rate is very slow (barely over 30/minute — such that we only see 4 beats). The R-R interval looks to be the same between the first 3 beats — but beat #4 looks like it occurs early (It also appears that QRS morphology of beat #4 is different from that of the first 3 beats).
  • P waves are present. That said — it is hard to tell from simple inspection of the rhythm if the atrial rate is (or is not) regular.
  • As to whether P waves are Related to neighboring QRS complexes? — We need to look in front of each of the 4 QRS complexes. It certainly appears that the PR interval in front of each of the 4 beats in the long lead II rhythm strip is different.

My Initial Impression of Rhythm-A:
I was not certain about the etiology of this rhythm.
  • Confession: Even after having had LOTS of time to contemplate Rhythm-A — I am still not sure what is going on. Obviously — some form of severe heart block is present. Pacing is likely to be needed unless something "fixable" is quickly found. That said — I admittedly had more questions than answers about this rhythm.

Looking closer ...
  • Does beat #4 occur early? To answer this question — I carefully measured each R-R interval in the long lead II rhythm strip (See Figure-7).

Figure-7: Caliper measurements of each R-R interval.


ANSWER: Beat #4 clearly does occur early.
  • PEARL #4: Most of the time when there is significant AV block — the BEST clue that a beat may be conducted is if a beat occurs earlier-than-expected. As a result — I wondered if beat #4 might be conducted by the P wave that appears in front of this beat?

  • NOTE #6: It's important to realize that we have no idea of how long the pause was before beat #1 — nor do we have any idea of when beat #5 occurred (or if beat #5 occurred at all?). 


Next QUESTION:
  • Are P waves regular in Rhythm-A?

In Figure-8 — I show my attempt to answer this question ...

Figure-8: I've labeled those P waves that we clearly see in Rhythm-A with RED arrows.

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ANSWER: As for PEARL #1 that we applied when problem-solving Rhythm-B — Using calipers facilitates (and expedites) predicting where additional P waves might be hiding.
  • PINK arrows in Figure-9 suggest logical "hiding spots" for the 3 missing P waves in Rhythm-A. Therefore, it is likely that the atrial rhythm is regular — and that 2 of the on-time sinus P waves are hidden within the QRS complexes of beats #1 and 3, with a 3rd P wave accounting for slight increase in the volume of the T wave of beat #2.

Figure-9: I've added PINK arrows to show where my calipers suggest that on-time P waves are likely to be hiding.


Putting It All Together for Tracing-A:
I admit to not being certain of the etiology of Rhythm-A.
  • PEARL #5: As disappointing as my admission of not being certain about the interpretation of Rhythm-A might be — there is an important lesson in this admission: The etiology for every rhythm will not always be evident from a single short period of monitoring (ie, We only see 4 beats in Rhythm-A — so it is understandable that we might not yet appreciate what is going on). 
  • Awareness that more information (ie, a longer period of monitoring) is needed — is an important concept to become comfortable with. 

What We DO Know about Rhythm-A:
The above said — We do know a lot about Rhythm-A:
  • At the least — there appears to be high-grade 2nd-Degree AV Block in Rhythm-A, with a very slow "escape" rate (just over 30/minute).
  • Beat #4 occurs early and manifests a different QRS morphology compared to the first 3 beats. As per PEARL #4 — the earlier-than-expected occurrence of beat #4 usually suggests that this beat may be conducted. That said — 2 findings are present in Rhythm-A that are against beat #4 being conducted. These findings are: i) That the PR interval preceding beat #4 in the long lead II rhythm strip looks surprisingly shorter than I would expect being able to conduct given how severe the AV block otherwise seems; and, ii) QRS morphology in simultaneously-recorded leads V4,V5,V6 for beat #4 looks much more like ventricular than conducted beats (ie, the wide QS complexes).
  • BUT — None of the P waves before beat #4 appear to have any relation to neighboring QRS complexes.

BOTTOM Line for Tracing-A: Whether beat #4 is conducted — or whether instead there is complete AV block with slightly early "escape" from another ventricular focus in the form of beat #4 is not apparent from this single tracing. What is known:
  • There is at-the-least high-grade 2nd-degree AV block with a very slow "escape" rate. As a result — pacing will be needed unless some "fixable" etiology for this slow rate can be found.
  • Although wide — QRS morphology for the first 3 beats looks like it is arising from somewhere within the conduction system (perhaps from the His — with RBBB conduction based on the QR pattern with predominant positivity in lead V1).
  • The deep Q in lead V1 — and the very deep T wave inversion in anterior leads suggests anterior infarction at some time in the recent past may be the reason for the severe AV block.
  • More information (and a longer period of monitoring) is needed to say more.


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Acknowledgment: My appreciation to Adem Ahmed (from Nouakchott, Mauritania) for the case and this tracing.

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Additional Relevant ECG Blog Posts to Today’s Case:

  • ECG Blog #185 — Use of a Systematic Approach to Rhythm Interpretation.
  • ECG Blog #191 — Is AV Block Complete? (Assessing AV Dissociation).


Other Posts on Assessing for AV Block:

— NOTE: There are even more cases relevant to assessment for AV Block on this Blog, but those below provide some “practice” for those in search of some example cases.



ADDENDUM:
  • What follows below is a 7-page excerpt from my ACLS-2013 Arrhythmias (Expanded Version) book, in which I review the distinction between AV dissociation vs complete AV block.


—  —

Today’s ECG Media PEARL #19a (6:45 minutes Audio) — Why is this Not Complete AV Block? This recording suggests a few Quick-Things-To-Do that help to rule in or rule out Complete AV Block (P.S. — I updated this Audio Pearl on 10/12/2021).






ECG Media Pearl #8 (8:20 minutes Video) — ECG Blog #191 — Distinguishing between AV Dissociation vs Complete AV Block (2/6/2021).




ECG Media Pearl #9 (5:40 minutes Video) — ECG Blog #192 — Reviews the 3 Causes of AV Dissociation (2/9/2021).





















Posted by ECG Interpretation at 4:23 PM 0 comments
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