Saturday, December 3, 2022

ECG Blog #348 — A 14yo with Palpitations

The 3 non-consecutive rhythm strips shown in Figure-1 — were obtained from a 24-hour Holter monitor, that was done on an athletic young teenage boy. The patient had a history of palpitations occurring both at rest and with activity. These 3 rhythm strips were representative of frequent arrhythmic activity that was seen during the course of 24-hour monitoring. An Echo on this patient was normal.

  • How would YOU interpret these rhythm strips? Do the widened beats in A and C represent short runs of NSVT (Non-Sustained Ventricular Tachycardia)?
  • Given the above history — What is the likely diagnosis? 
  • What treatment options should be considered?  

Figure-1: Non-consecutive rhythm strips obtained from a 24-hour Holter monitor — done on a young teenage boy with palpitations. (NOTE: — I do not have information on which leads were monitored in these tracings.

MY Thoughts on the ECG in Figure-1:
As per ECG Blog #185 — I favor the Ps, Qs, 3R Approach for interpretation of the cardiac rhythm — beginning with whichever of these 5 parameters is easiest to assess for the tracing in front of me:
  • PEARL #1: The 3 rhythm strips in Figure-1 show obvious variation with clear irregularity. Whenever I see a complex arrhythmia that contains different elements (some of which appear to be easier than others to interpret) — I always begin with the easier parts of the rhythm to interpret. Doing so often reveals the underlying rhythm — which then often facilitates interpreting the more difficult parts of the tracing.

The “EASIEST” Place to Start in Figure-1:
The closest thing to an underlying sinus rhythm appears in Rhythm B. I suspect that the upper rhythm strip in each of the 3 tracings in Figure-1 (which is in RED) — is a standard lead II. If this is the case — then we are seeing normal-looking and upright P waves with a normal PR interval in front of beats #1, 4 and 5 — which means that the underlying rhythm is sinus (RED arrows in Rhythm B — as shown in Figure-2).
  • Still looking at Rhythm B — The shape of the P waves in front of beats #3, 6, 7 and 8 looks slightly different than the shape of the P waves in front of beats #1,4,5 (PINK arrows highlighting slightly smaller P waves). The challenge is trying to determine if some (or all) of these PINK-arrow P waves represent sinus P waves (with some of the normal variation in sinus P wave morphology that is commonly seen due to artifact, movement, or random variation) — vs — P waves arising from another atrial focus.

  • Looking next at Rhythm C in Figure-2: The difference in P wave size and shape between the RED-arrow P wave (before beat #9 in C) — vs the PINK-arrow P waves (before beats #1,8,11) — looks to be real! So at this point — I was thinking that the underlying rhythm in today’s tracing was sinus — and that there was ectopic atrial activity.

  • Rhythm A in Figure-2 further supports this impression — with greatest difference in P wave size between the PINK-arrow P wave (before beat #16) — and the RED-arrow P waves (before beats #1,6,11 — which look to be larger in both monitoring leads of Rhythm A).

Figure-2: I’ve labeled definite atrial activity with PINK and RED arrows. At this point in my interpretation — I suspected that the underlying rhythm was sinus — with lots of ectopic atrial activity (See text).

The BLUE Arrows in Figure-3:
Keeping the important concept from PEARL #1 in mind (ie, To save interpretation of the more difficult parts of the tracing for last) — I now focused my attention on beat #2 in Rhythm B.
  • Now looking at Figure-3 — In Rhythm B, beat #2 is seen to occur earlier than one would expect. The QRS complex of this beat looks identical to each of the 7 other beats in Rhythm B — and — the BLUE arrow preceding beat #2 highlights a premature P wave. Therefore — beat #2 in Rhythm B is a PAC (Premature Atrial Contraction).

PEARL #2: I find the saying, "Birds of a Feather Flock Together" — to be an extremely helpful reminder of an important concept in arrhythmia interpretation. 
  • The meaning of this English proverb, "Birds of a Feather ..." — is that people of similar type, interest or character tend to mutually associate.

  • The relationship to cardiac arrhythmias of the saying, "Birds of a Feather" — is that IF we see other clear evidence on an arrhythmia of a frequent-occurring phenomenon — then additional less evident findings in that same patient probably reflect the same phenomenon.

  • For Example: Since we know that the BLUE arrow preceding beat #2 in B highlights a PAC — and, since other PINK arrows in Figure-3 all appear to represent some form of ectopic atrial activity — it is likely that the deflections highlighted by the 4 other BLUE arrows in this figure (seen over the small deflections between the run of rapid beats in Rhythm A) — also represent ectopic atrial activity. Therefore — beats #11-thru-15 in Rhythm A almost certainly represent a 5-beat run ATach! (Atrial Tachycardia).

NOTE: Although we might expect that a run of ectopic ATach should manifest similar beat-to-beat P wave morphology — it turns out that P wave morphology (as well as the P-P interval) may vary with ATach. This is especially true at the onset of ATach episodes, when additional ectopic atrial sites may initially be participating.
  • We have already seen some variation in P wave shape for a number of the PINK arrows in today's tracing. 

The YELLOW Arrow in Figure-3:
Let's complete our study of Figure-3 — with a look at the deflection highlighted by the YELLOW arrow in Rhythm C.
  • Beat #10 in Rhythm C is clearly early (ie, premature) — and, beat #10 is preceded by a premature P wave (ie, under the YELLOW arrow). Therefore — beat #10 in Rhythm C is a PAC.
  • Note that the QRS complex of beat #10 in C looks different compared to each of the other QRS complexes preceded by a colored arrow in Figure-3. The reason for this — is that beat #10 in C is aberrantly conducted. As per the Ashman Phenomenon — the fact that beat #9 in C is preceded by a relatively long R-R interval, sets up conditions for aberrant conduction by prolonging the subsequent relative refractory period (See ECG Blog #70for full discussion of the Ashman Phenomenon).
  • IF I am correct that the upper recording in rhythm strips A, B and C represents a standard lead II — then predominant negativity of the slightly widened QRS preceded by the YELLOW arrow for beat #10 in Rhythm C is consistent with LAHB (Left Anterior HemiBlock) aberration.

Figure-3: Blue arrows highlight ectopic atrial activity (including a 5-beat run of ectopic ATach in Rhythm A). The YELLOW arrow in C highlights that beat #10 is an aberrantly conducted PAC (See text).

  • What then are the WHITE arrows in Figure-4 pointing to?

Note that a subtle (very-small-but-definitely-present) deflection appears under each of the WHITE arrows that I have added in Figure-4.
  • No QRS complex follows these WHITE arrows.
  • By the "Birds of a Feather" concept — since colored arrows provide ample evidence of ectopic atrial activity (including PACs) throughout today's tracing — these WHITE arrows in Figure-4 almost certainly highlight non-conducted (ie, "blocked") PACs, that are occurring during the absolute refractory period.

Figure-4: WHITE arrows highlight blocked PACs.

The Last 2 YELLOW Arrows in Figure-5:
It's finally time to address the more difficult part of today's tracing — which is to determine the etiology of the two 4-beat runs of widened and different-looking QRS complexes (ie, beats #7-thru-10 in Rhythm A — and beats #2-thru-5 in Rhythm C).
  • PEARL #3: As emphasized in ECG Blog #211 — the most definitive criterion for diagnosing aberrant conduction, is to identify a premature P wave before the abnormal-looking beat or beats. This is precisely what each of the YELLOW arrows in Figure-5 do!

BOTTOM Line: The short runs of wide and different-looking beats in today's tracing do not represent runs of non-sustained VT. Instead — today's tracing shows an underlying sinus rhythm with multiple ectopic P waves.
  • Many of these ectopic P waves occur early (ie, as PACs). Some of these PACs are conducted normally — while others are aberrantly conducted (ie, those that follow the YELLOW arrows). Other PACs are blocked (ie, those highlighted by WHITE arrows).
  • Some ectopic P waves do not occur early (ie, the PINK arrows before beats #3, 6 and 7 in Rhythm B — and the PINK arrow before beats #8 and 11 in Rhythm C).
  • Finally — there are 3 runs of ATach, each consisting of 4-5 beats. Two of these runs manifest QRS widening as a result of aberrant conduction (ie, beats #7-thru-10 in Rhythm A — and beats #2-thru-5 in Rhythm C). The remaining run of ATach manifests normal conduction (ie, beats #11-thru-15 in Rhythm A).

Figure-5: YELLOW arrows highlight PACs that precede abnormal-looking beats in today's tracing. This confirms that the different-looking beats that follow these YELLOW arrows are all aberrantly conducted!

Putting It All Together:
Reviewing the details of today's case — The patient is an athletic teenager who presents with a history of palpitations occurring both at rest and with activity. An Echo was unremarkable. Holter monitoring over 24 hours revealed frequent episodes similar to those seen in rhythm strips A, B and C.
  • As emphasized above — this patient does not have ventricular tachycardia. Instead — the rhythm is sinus with multiple ectopic atrial activity, including frequent short runs of Atrial Tachycardia.

  • PEARL #4: Before accepting a primary arrhythmia diagnosis for the ECG findings in today's case — one needs to rule out underlying "fixable" causes of excess ectopic atrial activity. This might include some basic lab tests (to ensure a normal blood count, serum electrolyte and thyroid studies) — and ruling out extra-cardiac factors such as alcohol or stimulant drug use (ie, sympathomimetics, amphetamines, cocaine) — as well as factors such as excess anxiety, dehydration, sleep deprivation. In today's case — None of these potentially "fixable" factors were operative.

EAT (Ectopic Atrial Tachycardia):
The above evaluation leaves EAT as the most likely diagnosis for the teenage patient in today's case. (Although P wave morphology does show some variation in today's rhythm — MAT is exceedingly rare in children — so EAT is the most likely diagnosis).
  • Although overall, EAT is not often seen in children — it nevertheless is the most common cause of "incessant" SVT in the pediatric age group. In children, this rhythm is usually "idiopathic" (ie, without known cause).
  • An important complication of EAT to be aware of — is tachycardia-induced cardiomyopathy. It is for this reason that early recognition of EAT is especially important — since depending on the duration of this condition until diagnosis, the cardiomyopathy may or may not be reversible.
  • The "good news" regarding today's case — is that this patient's Echo was normal (such that there was no indication of a developing cardiomyopathy!).

  • In the ED (Emergency Department) — Adenosine can be diagnostic of EAT, because it produces transient AV block that may clearly show the underlying atrial tachycardia. That said — Adenosine doesn't convert EAT. An additional problem — is that EAT does not always respond to other antiarrhythmic drugs, or even to cardioversion.
  • EAT may respond differently in younger vs older children (Michel et alFront. Pediatr: Vol. 8; Article 313 — June, 2020 — and Kang et al Circulation: Arrhythmia and Electrophysiol 7:664-670, 2014). In children less than 3 years of age — EAT is more likely to spontaneously resolve. It is also more likely to respond to medication (ie, with a ß-blocker and/or IC agent).
  • In contrast — EAT is less likely to respond to medication, and less likely to spontaneously resolve in older children.
  • Definitive therapy of EAT is with RF (RadioFrequency) Ablation. Because of the better response to medical therapy, and the much greater chance of spontaneous remission — RF ablation is often delayed in younger children.

  • Regarding Today's Case: I do not have specific follow-up in today's case. That said — given the relatively older age of this pediatric patient, and the very frequent episodes of ATach (ie, producing an apparent "incessant" tachycardia) — referral to EP cardiology for ablation may ultimately be needed


Acknowledgment: My appreciation to Najlae Kourireche (from Marrakech, Morocco) for the case and this tracing.



Relevant ECG Blog Posts to Today’s Case:

  • ECG Blog #185 — Reviews my System for Rhythm Interpretation, using the Ps, Qs & 3R Approach.

  • ECG Blog #140 — Example of alternating Bifascicular Block Aberration.
  • ECG Blog #14 — Example of Blocked PACs.
  • ECG Blog #15 — Example of an aberrantly conducted WCT rhythm.
  • ECG Blog #33 — Example of PACs with varying degrees of Aberrant Conduction.
  • ECG Blog #263 — Differentiation of WCT rhythms (ie, deciding between VT vs Aberrancy?).
  • ECG Blog #211 — WHY does Aberrancy occur? (And why the most common form of aberrant conduction manifests RBBB morphology).

  • ECG Blog #70 — Reviews the Ashman Phenomenon (re aberrant conduction).
  • ECG Blog #71 — Regarding the Ashman Phenomenon with Atrial Fibrillation.

  • ECG Blog #204 — Reviews the ECG diagnosis of the Bundle Branch Blocks (RBBB/LBBB/IVCD).
  • ECG Blog #203 — Reviews ECG diagnosis of Axis and the Hemiblocks. For review of QRS morphology with the Bifascicular Blocks (RBBB/LAHB; RBBB/LPHB) — See the video ECG Video Pearl #21 in this blog post. 
  • ECG Blog #220 — Reviews My List for the Causes of a Regular WCT Rhythm (with Audio Pearl on assessing for hemodynamic stability)
  • ECG Blog #240 — Reviews the Case of a Regular SVT (SupraVentricular Tachycardia) Rhythm — with emphasis on how Rate of the rhythm may help in SVT diagnosis.


ADDENDUM (12/3/2022):

I have added supplementary material below regarding the ECG diagnosis of Aberrant Conduction.

ECG Media PEARL #28 (4:45 minutes Video) — Reviews WHY some early beats and some SVT rhythms are conducted with Aberration (and why the most common form of aberrant conduction so often manifests RBBB morphology).

  • NOTE: I have excerpted a 6-page written summary regarding Aberrant Conduction from my ACLS-2013-ePub. This appears below in Figures-6-7, and -8).
  • CLICK HERE — to download a PDF of this 6-page file on Aberrant Conduction.



Figure-6: Aberrant Conduction — Refractory periods/Coupling intervals (from my ACLS-2013-ePub).


Figure-7: Aberrant Conduction (Continued) — QRS morphology/Rabbit Ears.


Figure-8: Aberrant Conduction (Continued) — Example/Summary.


Monday, November 28, 2022

ECG Blog #347 — Why Non-Conducted P Waves?

The lead III rhythm strip shown in Figure-1 — was obtained from an older woman following a syncopal episode. Her 12-lead ECG showed QRS widening in a nonspecific IVCD (IntraVentricular Conduction Defect) pattern — but did not suggest acute coronary occlusion. The patient was hemodynamically stable at the time the rhythm strip in Figure-1 was recorded.

CHALLENGE Questions:

Which one (or more) of the following choices is (are) correct?
  • A normal sinus rhythm is present.
  • There is AFib (Atrial Fibrillation). 
  • AV dissociation is present.
  • 3rd-Degree AV Block is present.
  • Some type of Wenckebach conduction is present.

Figure-1: Long lead III rhythm strip — obtained from an older woman with syncope. How would YOU interpret the rhythm?

  • NOTE #1: As always — I favor the Ps, Qs & 3R Approach for interpretation of the cardiac rhythm (See ECG Blog #185). Assessment of these 5 parameters provides us with answers to the above Challenge Questions — and greatly narrows the possibilities for the rhythm diagnosis.

  • NOTE #2: Today’s tracing is slightly angled (slanted) — and as a result, measurements are slightly “off”. That said — this did not affect my overall interpretation of today's rhythm.

Is AFib Present? — OR — Is there Sinus Rhythm?
P waves are definitely present in Figure-1 — which rules out the possibility of AFib. It’s clear that more than a single P wave is present within some of the R-R intervals — so a simple “sinus rhythm” is not present.

Is AV Dissociation Present?
AV dissociation is defined as the absence of any relationshipship between P waves and QRS complexes. This can be complete AV dissociation (in which case none of the P waves in the entire rhythm strip are related to any of the QRS complexes — as occurs with complete AV block) — or AV dissociation can be transient (that is, "intermittent" — or only occurring for one or more beats, but not for the entire tracing).
  • Although at first glance it might seem as if there is AV dissociation in today's rhythm — a LOOK at Figure-2 reveals that this is not the case. WHY do I say this? 

  • HINT: What do the colored lines in Figure-2 suggest?

Figure-2: Why do the colored lines in this figure tells us that AV dissociation is not present?

Why AV Dissociation is Not Present:
Although the rhythm is not regular in Figure-2there is a pattern to this rhythm (ie, there is a "regular irregularity" to the rhythm). Thus, there is "group" beating (ie, alternating shorter-then-longer R-R intervals).
  • Note that each of the shorter R-R intervals in Figure-2 (BLUE lines) — are of approximately equal length.
  • Each of the longer R-R intervals (RED lines) — are also of similar (if not the same) length. This is not by chance!

PEARL #1: As emphasized in ECG Blog #186 — Whenever you see group beating in a rhythm — Consider the possibility of some type of Wenckebach conduction!
  • The type of Wenckebach conduction that most providers are familiar with — is 2nd-degree AV Block of the Mobitz I Type — in which the PR interval progressively increases until a beat is dropped. Another name for Mobitz I = AV Wenckebach!

  • It's important to appreciate that there are many other examples of Wenckebach conduction! These include SA Wenckebach — AFib, AFlutter or ATach with Wenckebach conduction (in which there is group beating with Wenckebach periodicity) — junctional or ventricular rhythms with retrograde Wenckebach or with Wenckebach exit block — and many others.

  • PEARL #2: Although the specific mechanism for many of these types of Wenckebach conduction is complex (and beyond the scope of today's ECG Blog) — the "Take-Home" Point from today's post is to Consider some type of Wenckebach conduction whenever you see "group" beating
  • Wenckebach conduction will not always be present in such cases (ie, you can see group beating with other rhythms — such as atrial bigeminy or trigeminy) — but prompt recognition of group beating when it does occur will facilitate rapid identification of Wenckebach rhythms! 

Continuing with Figure-2:
Did YOU Notice the repetitive pattern of PR intervals in Figure-2?
  • Note that each of the shorter PR intervals in Figure-2 (YELLOW lines) — are of approximately equal length.
  • Each of the longer PR intervals (GREEN lines) — are also of similar length. This is also not by chance!

BOTTOM Line for Figure-2:
AV dissociation is not present in Figure-2 — because all P waves are related in some way to neighboring QRS complexes. We know this — because the length of the 2 different PR intervals that we see in this rhythm (highlighted by the YELLOW and GREEN lines) are constantly repeated! This means that there must be some type of conduction!
  • Since there is some type of conduction in Figure-2 — this rules out the possibility of 3rd-degree (complete) AV block! You can't have complete AV block IF there is some conduction.
  • Instead — the fact that we see group beating in Figure-2 (in the form of alternating shorter-then-longer R-R intervals) — means that some form of Wenckebach conduction is probably present!

Is the Atrial Rhythm Regular?
Take another LOOK at today's rhythm (ie, See Figure-3).
  • Is the atrial rhythm regular?

Figure-3: Take another LOOK at today's rhythm (which I've reproduced from Figure-1). Is the atrial rhythm regular? How can we tell?

PEARL #3: Wenckebach conduction is very commonly seen with both ATach (Atrial Tachycardia) and AFlutter (Atrial Flutter). Therefore — IF you see a fast and regular atrial rhythm in association with group beating — the underlying mechanism will usually involve some type of Wenckebach conduction.
  • As I so often emphasize — Using calipers speeds up your interpretation and makes it EASY to determine if the underlying atrial rhythm is (or is not) regular.
  • Find a place in the rhythm you are looking at where you can definitely see 2 P waves in a row (ie, Any of the longer R-R intervals in Figure-3 will do!). Set you calipers precisely to the distance between these 2 consecutive P waves — and it then becomes EASY to "walk out" P waves through the entire rhythm strip (ie, RED arrows in Figure-4).

PEARL #4: Once you've established that the atrial rhythm is regular — Determining the atrial rate provides an important clue to the type of atrial rhythm.
  • As explained in ECG Blog #210 — the Every-Other-Beat Method for determining the ventricular rate — works equally well for determining the rate of fast atrial rhythms.

Figure 4: RED arrows highlight that the atrial rhythm in today's tracing is regular! Application of the Every-Other-Beat Method facilitates determining the rate of the atrial rhythm. Note that it takes just under 5 large boxes to record 2 P waves (YELLOW numbers in this Figure). Therefore — HALF the atrial rate is a little faster than 300/5 ~60-65/minute — which means that the actual atrial rate in today's tracing is ~2X this rate or ~125/minute. This is consistent with an atrial tachycardia (The atrial rate is not fast enough to be AFlutter)

What We Do Know at This Point!
Although we have not yet determined the specific mechanism of today's rhythm — We have answered all 5 of the Challenge Questions:
  • There is neither AFib nor simple sinus rhythm. The presence of regular P waves rules out AFib. The rapid atrial rate (ie, at ~125/minute) with failure to conduct all P waves rules out a simple sinus rhythm. Instead — there is atrial tachycardia.
  • Group beating with 2 PR intervals that regularly repeat (as highlighted by the YELLOW and GREEN lines in Figure-2) — rules out 3rd-degree AV block and AV dissociation. Instead — these findings strongly suggest that some type of Wenckebach conduction is occurring.

  • PEARL #5: To Emphasize — the presence of Wenckebach conduction in association with either ATach or AFlutter does not necessarily indicate a pathological form of AV block! Instead — this may simply result from the rapid atrial rate (in which case it is possible that normal 1:1 AV conduction may resume once the rapid atrial rhythm resolves). Sometimes only clinical correlation and the passage of a little time will tell IF Wenckebach conduction that occurs in association with ATach or AFutter is (or is not) pathologic.
  • That said — the patient in Today's Case is an older woman who presented with the rhythm in Figure-1 following a syncopal episode. In addition — QRS widening from a nonspecific IVCD was present on her 12-lead tracing. Therefore — any form of AV conduction disturbance has to be considered pathologic until proven otherwise!

  • KEY "Take-Home" Message from Today's Case: The specific mechanism for today's rhythm is complex. Full understanding by primary providers is not essential for appropriate management. Instead — it would be fine to stop your interpretation after establishing that today's rhythm shows atrial tachycardia with some form of Wenckebach conduction in this older patient with syncope who clearly needs further evaluation (and who may ultimately need a pacemaker)
Beyond-the-Core: The Specific Rhythm
Looking closer at Figure-4, in which we highlight regularly-occurring P waves throughout the entire tracing in today's rhythm — Aren't there P waves that we know are not being conducted to the ventricles?
  • My answer to this question is proposed in Figure-5 — in which I highlight P waves that seem incapable of being conducted all the way to the ventricles (WHITE arrows in Figure-5).
  • This leaves us with alternate R-R intervals in which we see 2 consecutive RED-arrow P waves. It's hard to imagine that both of these consecutive RED-arrow P waves (that occur between beats #2-3; 4-5; 6-7 and 8-9) — could be conducting to the ventricles. HOW then can we explain this?

Figure 5: WHITE-arrow P waves seem incapable of being conducted to the ventricles. But HOW to explain what is going on with alternate R-R intervals in which there are 2 consecutive RED-arrow P waves?

Dual-Level AV Block:
In ECG Blog #259 — I discussed the concept of Dual-Level AV Block (See the ADDENDUM below for an Audio Pearl review of this concept). In brief — Wenckebach conduction may occur at more than a single level as atrial impulses exit out of the AV Node. This concept is easiest to illustrate by means of a laddergram (See Figure-6).
  • The atrial rhythm in the laddergram is illustrated by the regular vertical RED lines in the Atrial Tier.
  • The horizontal BLACK dotted line schematically divides the AV Nodal Tier into 2 levels, each conducting impulses with its own degree of AV Block.

  • WHITE-arrow P waves do not make it through the upper AV Nodal level. Note that there is alternating 2:1 and 3:2 Wenckebach conduction in this upper AV Nodal level.
  • PINK-arrow P waves make it through the upper AV Nodal level — but do not make it through the lower AV Nodal level.
  • RED-arrow P waves make it through both AV Nodal levels — and are conducted to the ventricles. Note that there is 3:2 AV Wenckebach conduction through this lower AV Nodal level. 

Figure-6: My proposed laddergram for the mechanism of today's rhythm (See text).

CASE Conclusion:
The laddergram in Figure-6 makes sense — because all P waves and all QRS complexes in this tracing are accounted for. The underlying rhythm is atrial tachycardia with dual-level Wenckebach conduction out of the AV node, manifesting alternating 2:1 and 3:2 conduction at the upper AV Nodal level — and 3:2 AV conduction at the lower level.
  • Clinically (as emphasized in the above Take-Home Message) — given the presentation of this patient with syncope, full evaluation of this older woman is indicated. Pending results — she may ultimately need permanent pacing (Unfortunately — I do not have specific follow-up on this case).

  • P.S.: For those wanting direction for how to derive a laddergram when there is dual-level AV Block — Please check out the Step-by-Step Laddergram illustration for a similar case in ECG Blog #259.

Acknowledgment: My appreciation to Nizar Jiris (from Kfar Yasif, Israel) for allowing me to use this case and these tracings.

Related ECG Blog Posts to Today’s Case: 

  • ECG Blog #185 — Reviews the Ps, Qs & 3Rs Approach to systematic rhythm interpretation.
  • ECG Blog #210 — Reviews the Every-Other-Beat Method for determining the rate of a fast regular rhythm.

  • ECG Blog #188 — Reviews the essentials for reading (and/or drawingLaddergrams, with LINKS to numerous Laddergrams I’ve drawn and discussed in detail in other blog posts.

  • ECG Blog #186 — Highlights the importance of Group Beating — and reviews when to suspect the Mobitz I form of 2nd-Degree AV Block ( = AV Wenckebach).

  • ECG Blog #251  Reviews the concepts of Wenckebach periodicity and the "Footprints" of Wenckebach (Please check out the Audio Pearl in this blog post that focuses on these concepts).
  • ECG Blog #164 — Reviews a case of typical Mobitz I 2nd-Degree AV Block (with detailed discussion of the "Footprints" of Wenckebach). 

  • ECG Blog #259 — Reviews the concept of Dual-Level AV Block.
  • The October 25, 2021 post in Dr. Smith's ECG Blog — My Comment (at the bottom of the page) reviews my approach to another case of a Dual-Level Wenckebach block. 
  • ECG Blog #226 — Works through a complex Case Study (including an 11:00 minute ECG Video Pearl that walks you through step-by-step in the construction of a laddergram with Wenckebach conduction and dual-level block within the AV node).
  • ECG Blog #243 — Reviews a case of AFlutter with Dual-Level Wenckebach out of the AV Node.


ADDENDUM (11/28/2022): 

  • For review on the concept of "Dual-Level" Wenckebach.

ECG Media PEARL #71 (5:45 minutes Audio) — Reviews the phenomenon of Dual-Level Wenckebach out of the AV Node (HOW to recognize this phenomenon — and how to distinguish it from Mobitz II).


ADDENDUM (11/29/2021): I received a comment today on this tracing from David Richley, who is well known to most ECG enthusiasts who frequent any of the many ECG internet forums. Dave always offers the most astute commentary on complex Arrhythmia interpretation. NOTE: What follows below goes beyond-the-core! — But — It illustrates the important concept that complex arrhythmias may have more than a single potentially plausible interpretation.
  • Dave writes the following: Hi KenI enjoyed your latest ECG blog (as always) — but while I agree that there is dual-level Wenckebach AV block — I could not explain why 2:1 block should alternate with 3:2 block in the upper AV node. What could be the physiological explanation for this? 
  • I’ve come up with a modification of your hypothesis: I think there could be 5:4 Wenckebach AV block in the upper AV node — then 2:1 block of those impulses that reach the lower AV node, as illustrated in this laddergram. What do you think? — Dave

Figure-7: Proposed laddergram submitted by David Richley.

MY Reply to Dave:
  • Dave — I think both your laddergram and my laddergram are plausible. I always find it challenging with dual-level AV blocks — to try and figure out whether it is the upper or lower AV nodal level that has a higher degree of block. (Going back to some of the original articles on dual-level AV blocks — they describe even more than 2 levels of block within the AV node — so it can get even more complicated that what we see in today's rhythm).
  • As per my Figure-6 — those beats with shorter PR intervals (ie, beats #1,3,5,7,9) — are preceded by longer R-R intervals — so I thought that might allow more time to recover, therefore allowing better (faster) conduction through the lower AV nodal level. I fully acknowledge that I may be wrong ...

  • BOTTOM LINE: The KEY point is in your initial sentence, in which you state how we both agree that there is dual-level AV block. The geometric relationships (with repeating PR and R-R intervals) are not by chance — do not represent complete AV block — but rather manifest some variation of AV Wenckebach conduction. On this we both agree! THANKS again for your always superb insights Dave!