ECG Blog #202 — Do Any P Waves Conduct?

The long lead II rhythm strip in Figure-1 was obtained from an older patient with syncope. The rhythm was diagnosed as probable complete AV Block. 

• Do YOU agree with the diagnosis of complete (3rd-degree) AV Block?

 

Figure-1: Lead II rhythm strip, obtained from an older patient with syncope. Is this complete AV Block? (See text).

 

  

MY Approach to the Rhythm in Figure-1:

Unfortunately — the tracing is slanted, therefore slightly distorted. That said — we can still appropriately interpret this tracing. By the Ps, Qs & 3R Approach (See ECG Blog #185):

• The QRS is narrow (at least in this single monitoring lead).
• Taking into account the slanting, with slight distortion of the ECG paper — the ventricular rhythm overall looks to be regular with exception of beat #4 that occurs earlier-than-expected. 
• P waves are present. That said — it is difficult to tell from Figure-1 if the atrial rhythm is or is not regular ... At this point I reached for my calipers.
• NOTE: Before using my calipers — I thought it looked as if several (if not many) of the P waves seen in Figure-1 were not conducted. So, at the least — it seemed probable that some form of 2nd-degree AV Block was present.

  

 

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NOTE: Some readers may prefer at this point to listen to the 5-minute ECG Audio PEARL before reading My Thoughts regarding the ECG in Figure-1. Feel free at any time to review to My Thoughts on this tracing (that appear below ECG MP-19).

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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).

 

 

MY Approach to this Rhythm (Continued):

The benefit of using calipers becomes immediately apparent on review of Figure-2:

• I began by setting my calipers to the P-P interval suggested by any 2 consecutive P waves that I could be certain of (ie, One might use either the P waves seen before and after beat #4 — or — the P waves seen before and after beat #5). Doing so allowed me to find “on-time P waves” at all of the places highlighted by RED arrows.
• I highlight with WHITE arrows in Figure-2 the 2 places in this rhythm strip where I did not see clear indication of an underlying P wave.

PEARL #1: Most of the time when there is AV block — the atrial rhythm will be regular (or at least fairly regular if sinus arrhythmia or ventriculophasic sinus arrhythmia is present). Therefore, even though we do not see clear indication of sinus P waves under the WHITE arrows — the chances are excellent that on-time P waves are hiding within the QRS of beats #2 and 7.

• The subtle distortion at the onset of the QRS complex of beat #7 supports my presumption that there are regular P waves throughout this tracing (and the on-time occurrence of this subtle distortion almost certainly marks the beginning of a P wave that is mostly contained within the QRS of beat #7).
• Unfortunately — all we have in today’s case is this single lead II rhythm strip. But additional monitoring at the bedside and/or looking at simultaneously-recorded leads on a 12-lead tracing are 2 ways to confirm that regular P waves are indeed present!

 

Figure-2: I’ve labeled atrial activity in Figure-1 with RED arrows highlighting P waves I am certain of (See text).

 

QUESTION: 

• At this point in today’s case — HOW did YOU interpret this rhythm?

  

MY Thoughts Continued:

Based on the findings described above — we can diagnose the rhythm in Figure-2 as showing some form of 2nd-degree AV Block because: i) There are regular sinus P waves (so we are not dealing with PACs or sinus pauses in a patient with Sick Sinus Syndrome); and, ii) At least some of these P waves are not conducting. In addition — I would emphasize the following:

• The QRS is narrow everywhere — so the site of the ventricular escape rhythm is within the conduction system (ie, either at the AV node or in the His).
• PEARL #2: There is AV dissociation — since many P waves appear not to be conducting. But we can not establish the likely severity of AV block until we evaluate how many of these P waves have a reasonable chance to conduct, yet still fail to do so!
• PEARL #3: The fact that beat #4 occurs much earlier-than-expected in Figure-2 — strongly suggests that this P wave is being conducted! Most of the time with AV block — the ventricular escape rhythm will be regular (or at least, fairly regular). The BEST clue I know when assessing a rhythm to determine if any conduction is present, is to look for beats that occur earlier-than-expected! 
• NOTE: Unlike any other PR interval in this tracing — the PR interval before beat #4 (which measures ~0.19 second) is of a duration that could be expected to conduct. Do any of the other P waves on this tracing manifest a PR interval that gives them a reasonable chance to conduct?

 

LADDERGRAM:

The easiest way to convey my thinking is by drawing a laddergram (Figure-3). For clarity — I have labeled all P waves in this tracing.

• I’ve previously reviewed how to read (and draw) laddergrams (See ECG Blog #191). As I noted in Pearl #3 — the much-earlier-than-expected occurrence of beat #4 strongly suggests that P wave “g” is being conducted! As a result — the degree of AV block in this tracing is not complete!
• All other QRS complexes in this tracing appear to be junctional escape beats — because the R-R interval preceding each of these beats is constant (corresponding to an appropriate junctional escape rate of ~6 large boxes = ~50/minute) — and — none of the other P waves in this tracing have an adequate opportunity to conduct (ie, P waves b, d, f, i, k, m and o all occur too close to the QRS — and P waves a, c, e, h, j, l and n all occur quite far away from the next QRS).
• PEARL #4: Despite the fact that all P waves in this tracing except “g” do not conduct — there is no evidence to suggest “high-grade” AV block. This is because we never see 2 P waves in a row that should conduct, yet fail to do so! 

 

BOTTOM LINE: I would interpret this tracing as showing 2nd-degree AV Block of uncertain severity. There is evidence of 2:1 AV conduction (ie, every-other P wave that occurs near the middle of the R-R interval should conduct but doesn't) — but the 1 P wave that does conduct (ie, "g"), does so with a normal PR interval. So, it is very possible that the conduction ratio is no worse than 2:1.

• This most probably is 2nd-degree AV Block of the Mobitz I (AV Wenckebach) Type — because the QRS complex is narrow, and Mobitz I is so much more common than Mobitz II.
• As discussed in detail in ECG Blog #191 — AV dissociation is never a diagnosis, but instead always arises because of “something else” (ie, because of “usurpation”, “default”, or AV block). In today’ case — the reason for AV dissociation is 2nd-degree AV Block.
• The patient in today's case may or may not need a permanent pacemaker. We simply can not answer this question based solely on this single short rhythm strip — in which the overall heart rate never drops below 50/minute, and the degree of AV block is not complete. Additional rhythm monitoring (and correlation with the patient's symptoms) — will be needed to answer this question. 

 

Figure-3: Proposed laddergram for the rhythm in Figure-2 (See text).

 

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• Acknowledgment: My appreciation to Václav Lejsek (from Prague, Czech Republic) 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).
• ECG Blog #188 — How to Read (and Draw) Laddergrams.

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 example cases.

• ECG Blog #164 — On Mobitz I.
• ECG Blog #187 — Some Form of Wenckebach.
• ECG Blog #189 — Dual-Level Wenckebach.
• ECG Blog #192 — AV Dissociation by Default (vs Usurpation).
• ECG Blog #62 — 2:1 AV Block: Mobitz I or II?
• ECG Blog #61 — Vagotonic AV Block.
• ECG Blog #58 — AV Dissociation by “Default”.
• ECG Blog #66 — Group Beating not Due to Wenckebach.
• ECG Blog #154 — Group Beating with Acute Inferior MI.

ECG Blog #201 — Should the Cath Lab be Activated?

The ECG shown in Figure-1 was obtained from a woman in her 80s with a history of a recent stroke. She complained of epigastric discomfort while at rehabilitation. 

• Based on this ECG — Should the cath lab be activated?

 

Figure-1: ECG obtained on a woman in her 80s, complaining of epigastric discomfort. Should the cath lab be activated?

 

My Initial Thoughts on Seeing this Tracing:

I was initially concerned about potential marked ST elevation in leads I and II — as well as ST elevation to a lesser extent in lead aVL and in the chest leads. 

• I was struck by the finding of some elevation of the isoelectric line that begins before the QRS complex in these 2 leads with maximal ST elevation — which I thought looked similar to the appearance of a Spiked Helmet Sign (See LINK to Dr. Smith’s June 28, 2020 post below for my review of the Spiked Helmet Sign). 
• I thought both the shape and the distribution of the ST elevation in leads I and II of ECG #1 to be strange. That said — I thought cardiac cath might be needed to clarify the picture.

 

The Case Continues:

A 2nd ECG was done 30 minutes after ECG #1. For clarity — I show both of these tracings in the sequence as they occurred in Figure-2.

• Based on the 2 ECGs in Figure-2 — Do you still want to activate the cath lab?
• WHY or why not? 

 

Figure-2: The initial ECG, together with a repeat ECG done 30 minutes later (See text).

 

 

 

COMMENT:

The decision was made not to activate the cath lab. It was noted that the abnormal deflections seen in ECG #1 were no longer present in the repeat ECG done 30 minutes later (Figure-2). Among the investigations done at the time:

• A bedside Echo showed good LV function without wall motion abnormality.
• Troponin X3 was without meaningful elevation.
• A 3rd ECG done ~2 hours after ECG #2 remained unchanged from ECG #2.

 

QUESTION: How do YOU explain the change in appearance that we see in Figure-2 between ECG #1 and ECG #2?

 

 

ANSWER: In view of complete resolution of the abnormal ST-T wave deflections that were seen in ECG #1, along with the normal bedside Echo and negative serial troponins — it was felt that the deflections that had been seen in ECG #1 were the result of Artifact produced by contact of the RA electrode lead with a pulsating artery (sometimes known as "PTA" = Pulse-Tap Artifact).

 

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• CONFESSION: It is good to be humbled every now and then. I fully acknowledge that I initially missed the diagnosis in this case! In retrospect — I should have immediately recognized artifact as the cause — but I didn't ...

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DISCUSSION:

Today’s case provides an excellent example of how the 1st time you see an ECG phenomenon — it may pass unrecognized. But after one learns about the phenomenon — it becomes EASY to recognize in the future!

• I actually was well aware of the phenomenon of contact with a pulsating artery producing marked ST-T wave abnormality. But I had not previously seen as deceptive an example of this phenomenon as occurs in today’s case. Therefore — I fell into the “trap”.

 

PEARL #1: Artifact is common in clinical practice. The BEST way not to overlook artifact — is to be aware of how common it actually is! I’ll add the following points regarding today’s case:

• The 1st Clue to Artifact — is that the shape of the elevated ST segments is bizarre. It is unusually straight — and becomes surprisingly pointed at its peak in multiple leads. In the one lead in which the T wave is negative ( = lead aVR) — the deepest part of the inverted T wave is also surprisingly pointed. This is not physiologic. In general, when ECG deflections look bizarre and “unphysiologic” — there is an excellent chance that such deflections are not real!
• The location of these 2 limb leads showing maximal ST elevation ( = lead I and lead II) — is not anatomic for what should be expected with acute MI, especially in the absence of reciprocal ST depression in other limb leads. It’s hard to imagine what coronary artery might be occluded with ST elevation in the limb leads limited to leads I and II.
• The bizarre ST-T wave shape in all leads showing ST elevation (and also in lead aVR with T wave inversion) — occurs at a fixed interval with respect to the preceding QRS complex (Figure-3). This tells us that whatever is producing these deflections must be related to cardiac contraction (and/or to arterial pulsation)!

Figure-3: I’ve colored in maximal artifact deflections in RED — and lesser amplitude artifact deflections in GREEN (See text).

PEARL #2: The distribution of the bizarre ST-T wave deflections precisely follows the location and relative amount of amplitude distortion predicted by Einthoven’s Triangle.

• The bizarre ST elevation is approximately equal in 2 of the limb leads (ie, in leads I and II) — and, not seen at all in the 3rd limb lead (ie, no artifact at all is seen in lead III). By Einthoven’s Triangle (See the picture below for today’s ECG Media Pearl — which shows Einthoven’s Triangle in the righthand corner) — the finding of equal ST segment amplitude artifact in Lead I and Lead II, localizes the "culprit" extremity to the RA ( = Right Arm) electrode.
• The absence of any artifact at all in lead III is consistent with this — because, derivation of the standard bipolar limb lead III is determined by the electrical difference between the LL ( = Left Leg) and LA ( = Left Arm) electrodes, which will not be affected if the source of the artifact is the right arm.
• As I discuss in detail in my MP-18 Audio Pearl below — the finding of maximal amplitude artifact in unipolar lead aVR confirms that the right arm is the “culprit” extremity.

  

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Today’s ECG Media PEARL #18 (7:45 minutes Audio) — On recognizing Artifact — and — using Einthoven’s Triangle to determine within seconds the “culprit” extremity causing the Artifact on your ECG.

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NOTE: I reproduce below in Figures 4, 5 and 6 — 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 amplitude deflections when the cause of the artifact is a single extremity. These principles are illustrated by the colored deflections in Figure-3:

• 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 aVR in Figure-3 (RED outline of the inverted T wave in this lead); and, ii) The amplitude of the artifact in the other 2 augmented leads (ie, leads aVL and aVF) is about 1/2 the amplitude of the artifact in lead aVR (GREEN outline of the sharply angled ST-T waves in leads aVL and aVF).
• Similarly — the amplitude of the artifact deflections in the 6 unipolar chest leads in Figure-3 is also significantly reduced from the maximal amplitude seen in leads I, II and aVR (GREEN outline of the sharply angled ST-T waves in each of the 6 chest leads).

 

PEARL #3: A final important clue to artifact as the cause of the bizarre ST-T wave deflections we see in ECG #1 — is provided in the long lead II rhythm strip at the bottom of the tracing!

• Did YOU notice how the artifact comes and goes in this long lead II rhythm strip? Thus, we see maximal artifact in beats #2, 3, 9, 10 and 15 in this long lead II rhythm strip (including that baseline elevation distortion that begins just before the QRS complex of these beats — and which gives false impression of a spiked Helmet Sign).
• In contrast — there is no artifactual ST elevation at all in beats #5, 6, 12, 13 and 17 — and an intermediate amount of artifact distortion in the remaining beats. This changing amount of artifact from one-beat-to-the-next would be consistent with the RA electrode making only intermittent contact with the pulsating artery. I can not think of a physiologic reason other than artifact to explain this beat-to-beat variation in ST-T wave appearance.

 

BOTTOM LINE: You will see artifact frequently in real-life practice. With a little practice, you can immediately KNOW with 100% certainty that the bizarre deflections on a tracing like this one are the result of artifact, and are related to arterial pulsations in one of the extremities. 

• Nothing else shows 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 artifact at all 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-4: Page 475 from the Rowlands and Moore article referenced above (See text).

 

Figure-5: Page 476 from the Rowlands and Moore article referenced above (See text).

 

Figure-6: Page 477 from the Rowlands and Moore article referenced above (See text).

 

 

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Acknowledgment: My appreciation to 林柏志 = Po-Chih Lin (from Taiwan) for these tracings and this case.

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Additional Relevant ECG Blog Posts to Today’s Case:

• The June 28, 2020 post in Dr. Smith’s ECG Blog — for review of the Spiked Helmet Sign.  Please scroll down to the bottom of the page at this link to see My Comment.

Regarding ECG Recognition of ARTIFACT:

• ECG Blog #148 — Artifact simulating VFib.
• ECG Blog #44 — Artifact produced by Parkinsonian tremor
• ECG Blog #139 — Artifact simulating AFlutter. 
• ECG Blog #132 — More artifact simulating VT-VFib. 
• Brief review by Tom Bouthillet on some common causes of artifact.

Finally — I link to several illustrative Cases taken from Dr. Smith’s ECG Blog. For each of these posts — Please scroll down to the bottom of the page to see My Comment. These cases provide insight to assessment for ARTIFACT:

• The September 27, 2019 post in Dr. Smith’s ECG Blog — in which I use the Rowlands & Moore article, with the above-noted formulas for recognizing the “culprit” extremity.
• The October 17, 2020 post in Dr. Smith’s ECG Blog — for an example of VT-like artifact
• The January 30, 2018 post in Dr. Smith’s ECG Blog — for arterial pulsation artifact (Please click on the COMMENTS to this post to see my discussion).

Blog #200 — Wandering Pacemaker (vs MAT)?

There is no clinical information is available for the ECG and 2-lead rhythm strip shown below in Figure-1.

• HOW would you interpret this tracing?
• What treatment is likely to be needed? 

Figure-1: How would you interpret this ECG? (See text).

 

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Editorial Comment:

It is always challenging to interpret tracings without the benefit of clinical information. That said — this situation is common in clinical practice. My experience in this area derives from the 30 years during which I was charged with interpreting all ECGs ordered by 35 medical providers at a primary care clinic — as well periodic stints during which I interpreted hospital tracings without the benefit of any history. 

• The challenge lies with having to decide which tracings in the “pile of ECGs to be interpreted” were those for which I needed to pull the medical chart (or call the provider) because of ECG findings of immediate potential concern.
• Obvious time constraints made it impossible to pull the chart for each ECG that I was given to read (I’d never get anything else done if I did so).
• I therefore became well versed in the skill of limiting the charts that I would pull to those patients whose ECGs showed findings I thought were important and potentially indicative of an acute situation that may have been overlooked.

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MY Thoughts on the ECG in Figure-1:

As always — systematic interpretation of any ECG should begin with assessing the cardiac rhythm. In general — lead II and lead V1 are the 2 best leads on a 12-lead tracing for assessing atrial activity — and we have the advantage in Figure-1 of a simultaneously-recorded 2-lead rhythm strip of both of these leads. By the Ps, Qsand 3R Approach:

• The rhythm in Figure-1 is clearly irregular.
• The QRS complex is narrow (ie, not more than half a large box in duration = ≤0.10 second). 
• The rate varies from 50/minute — to just under 100/minute.
• More than 1 P wave morphology is present. That said — P waves do appear to be related to neighboring QRS complexes, because the PR interval for the P wave shapes that we see remains constant (See Figure-2).

 

Figure-2: I’ve labeled the different P wave shapes with different-colored arrows (See text).

 

MY Thoughts on Figure-2:

There are 2 different P wave shapes in Figure-2.

• The tracing begins with 3 sinus beats (ie, RED arrows highlight 3 similar-looking upright-in-lead-II P waves — all with the same PR interval).
• P wave shape then changes for beats #4, 5 and 6 (ie, BLUE arrows highlighting an almost isoelectric, if not negative P wave with fixed PR interval).
• The atrial focus then shifts back, with return to sinus P waves for beats #7, 8, 9 and 10 (ie, return of RED arrows highlighting similar-looking, upright P waves in lead II — albeit with variability in the R-R interval).
• The rhythm in Figure-2 concludes with a slowing-down of the ventricular rate, as the 2nd atrial focus returns, in which the P wave is almost isoelectric (ie, BLUE arrows for beats #11 and 12).

BOTTOM LINE regarding Figure-1: The rhythm in Figure-2 is most consistent with a Wandering Atrial Pacemaker. This is because the change from one atrial site to the next occurs gradually over a period of several beats.

Technically, for a rhythm to be classified as a wandering pacemaker — there should be gradual shift between at least 3 different atrial sites. Since we only see 2 different atrial sites (highlighted by RED and BLUE arrows) in Figure-2 — we would need a longer period of monitoring to prove this rhythm is a wandering pacemaker. That said — wandering pacemaker is the most logical explanation for this rhythm. In support of this conclusion — the rest of the 12-lead ECG looks benign, consistent with the common finding of wandering pacemaker as a type of normal variant occurring most often in asymptomatic, otherwise healthy young adults. No treatment is needed for this rhythm. So, even though we have not been provided with any clinical history on this patient — I would be comfortable concluding that the ECG in Figure-2 looks benign.
• PEARL: The reason it is uncommon (if not rare) in clinical practice to see a wandering atrial pacemaker — is that most providers do not pay long enough attention to beat-to-beat change in P wave morphology needed to identify gradual shift between at least 3 different atrial sites.

 

SUMMARY: Review of the KEY features of wandering atrial pacemaker is the theme below for our ECG Media Pearl #17 (a 3:30 minute audio recording).

• Written review of wandering pacemaker appears below in Figure-3.
• Review of MAT is covered in our ECG Blog #199.

 

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Today’s ECG Media PEARL #17 (3:30 minutes Audio) — What is a Wandering Atrial Pacemaker (as opposed to MAT)?

 

 

Figure-3: Written review of wandering atrial pacemaker.

ADDENDUM (3/4/2021):

I received the following note from David Richley regarding today’s tracing: “I think I would use different terminology to describe this because to me the atrial pacemaker doesn’t so much ‘wander’ as ‘jump’. I would describe this as sinus arrhythmia with junctional escape rhythm at 60-65/minute every time the sinus node discharge rate slows to below that rate. I interpret the escape beats as junctional rather than atrial, because athough the P waves, (which are initially negative in II, aVF and V4-V6 — and positive in aVR) precede the QRS — the PR segment is very short, suggesting an AV nodal origin. However, we describe this phenomenon — I do agree that it’s likely to be completely benign.

 

MY Thoughts: Dave’s comment is one of the reasons why: i) The diagnosis of wandering pacemaker requires clear demonstration of shift in the atrial pacemaker in at least 3 different sites. We only see 2 different sites here; and, ii) The diagnosis of wandering atrial pacemaker is not common. 

• It’s impossible to rule out Dave’s theory from the single tracing we have.
• That said — the BLUE arrow P wave site may or may not be of AV nodal origin (you can see a similar, near-isoelectric P wave with short PR interval from a low atrial site).
• I also considered the possibility of the BLUE arrow P waves representing junctional escape — but decided against it because the difference in R-R interval from what we see between beats #9-10 vs what we see between beats #10-11 is more than what I’d expect based on the cadence of rate variation I see from beats #7-10.
• Bottom Line: We both agree there is a shift in the pacemaker site in a rhythm that is likely to be benign. And, we both agree that additional monitoring would be needed for a definitive response. THANK YOU Dave!

Blog #199 — AFib - MAT - Wandering Pacer - PACs

The ECG in Figure-1 was obtained in the ED from an older man with a long smoking history. He presented with acute shortness of breath. 

• What is the rhythm?
• Is this an unexpected finding in this type of patient?
• Could this be a wandering atrial pacemaker?
• WHY is it important to recognize the rhythm in Figure-1?

 

Figure-1: ECG obtained from an older man with a long smoking history — who presented with acute shortness of breath (See text).

 

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NOTE #1: Some readers may prefer at this point to watch the 3:20-minute ECG Video before reading My Thoughts regarding the rhythm in Figure-1. Feel free at any time to review to My Thoughts (that appear below ECG MP-16).

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Today’s ECG Media PEARL #16 (3:20 minutes Video) — What is MAT (Multifocal Atrial Tachycardia)? ECG Recognition — What to do about it — How to distinguish from a Wandering Pacemaker ...

 

 

 

 

 

MY Approach to Assessing the ECG in Figure-1:

We are only given a single lead rhythm strip to assess. That said — this should be sufficient for accurate interpretation:

• The rhythm is rapid — and irregularly irregular.
• The QRS complex is narrow.
• P waves are present. Looking closely — P wave morphology (and the PR interval) appear to be changing constantly!

IMPRESSION of the Rhythm: By far — the most common cause of an irregularly irregular supraventricular (narrow QRS) rhythm is AFib. The fact that P waves are present rules out AFib as the diagnosis.

• In order to clarify our observation that P waves are present but constantly changing in shape and in their PR interval — we have labeled the different shapes of P waves in different colors in Figure-2:

 

Figure-2: I have labeled the different P wave shapes from Figure-1 with different colors (See text).

 

My Assessment of Figure-2: Realizing that we only have a single lead to assess — and realizing that there are some artifactual undulations in the baseline — it should be apparent that there are multiple different P wave morphologies in Figure-2:

• Virtually all P wave shapes in Figure-2 are positive — albeit some P waves are almost equally biphasic (RED arrows). The PINK arrow highlights a P wave which is biphasic, but with a tiny and slender negative component.
• YELLOW P waves highlight pointed P waves — GREY P waves are peaked but a little less pointed — and ORANGE P waves are peaked but much smaller.
• BLUE P waves are tiny, if not isoelectric.
• The GREEN and PURPLE P waves look rounder — and are partially hidden at different points within the ST segment.

BOTTOM LINE: The rhythm in Figure-2 is MAT (Multiple Atrial Tachycardia). I'd emphasize the following:

• MAT is not a common diagnosis. As a result, in order to differentiate MAT from the much more commonly encountered irregularly irregular rhythm (which is AFib) — we need to be certain we are seeing multiple different P wave morphologies that are constantly changing. The colored arrows in Figure-2 make it evident that we are! 
• MAT almost always occurs in one of 2 common predisposing settings. These 2 settings are: i) In patients with severe, often longstanding pulmonary disease; and/or, ii) In acutely ill patients with multi-system disease (ie, sepsis, shock, electrolyte and/or acid-base disorders). As a result — I’m hesitant to diagnose MAT in the absence of one of these 2 settings. The fact that the patient in today’s case is a long-term smoker who presents with acute dyspnea is therefore in support of the diagnosis of MAT.
• PEARL: It is EASY to overlook the diagnosis of MAT because: i) The diagnosis is not common; and, ii) P waves with changing morphology may not always be evident in all 12 leads — so IF the 1 lead you are monitoring happens to be one in which P waves are not well seen — then you might assume the irregular rhythm in front of you was AFib. 12 leads are better than one! It is especially important to always obtain a 12-lead ECG whenever you see an irregularly irregular rhythm in association with one of the 2 predisposing conditions that MAT is pront to occur in.
• MAT is not a Wandering Pacemaker. MAT is a pathologic rhythm in which P wave morphology changes from one-beat-to-the-next. In contrast — a wandering pacemaker is often a benign rhythm (if not a normal variant) — in which there is gradual shift in P wave morphology over a period of several beats, most often occurring in an otherwise healthy and asymptomatic patient.
• The importance of recognizing MAT — is that treatment is different than the treatment of AFib. Most of the time, the heart rate with MAT will not be excessive — so all that is usually needed is to identify and correct the underlying predisposing cause (ie, optimize oxygenation; treat sepsis, electrolyte or acid-base disorders). This is distinctly different than treatment objectives for AFib, which in addition to correcting the cause — consist of rate slowing and medical or electrical cardioversion interventions.

 

Beyond-the-Core: There are 2 additional advanced ECG findings in the lead II rhythm strip from today’s case:

• A number of P waves that occur at an early point within the ST segment are non-conducted. In Figure-2 — these include P waves highlighted by the 1st BLUE arrow — the 2 ORANGE arrows — and the PURPLE arrow. (NOTE: I acknowledge one could argue that the 2nd ORANGE arrow is an r’ rather than a P wave).
• The QRS complexes of beats #3, 7, 12 and 16 are all somewhat smaller in amplitude than the other QRS complexes. I suspect the reason for this, is aberrant conduction that is facilitated by the Ashman phenomenon — since each of these beats manifest a relatively short coupling interval — and — each of these beats follow a relatively longer preceding R-R interval (For detailed explanation of the Ashman Phenomenon — See ECG Blog #70).

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• NOTE: For a Summary of KEY points related to MAT — See Figure-3 below.

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Additional Relevant ECG Blog Posts to Today’s Case: 

• ECG Blog #65 — for an example of MAT in a patient with chronic pulmonary disease (plus more on the differential diagnosis of MAT).
• ECG Blog #200 — for an example of Wandering Atrial Pacemaker.

I link to 2 additional illustrative Cases taken from Dr. Smith’s ECG Blog. For each of these posts — Please scroll down to the bottom of the page to see My Comment. These cases provide insight to assessment for MAT:

• The January 5, 2020 post in Dr. Smith’s ECG Blog — for an example of MAT.
• The September 30, 2019 post in Dr. Smith’s ECG Blog — for an example of “MAT”, but without the tachycardia ...

 

Figure-3: Summary of KEY points related to MAT.