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 #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. 

==================================

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.