ECG Interpretation: 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).

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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.

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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 #70 — for 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).

QUESTION:

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

ANSWER:

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 al — Front. 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.

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

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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.

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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.