Sunday, March 8, 2026

EXTRA COPY- ECG Blog #522 — What is the "Other" Diagnosis? — EXTRA COPY



The ECG in Figure-1 is from a middle-aged man who presented to the ED with new-onset severe CP (Chest Pain). His symptoms lasted ~30 minutes — but his CP had totally resolved by the time this ECG was recorded.


QUESTIONS:
  • How would you interpret the ECG in Figure-1?
    • What would you do?

Figure-1: The initial ECG in today's case — obtained from middle-aged man with new CP. His CP had resolved by the time this ECG was recorded (To improve visualization — I've digitized the original ECG using PMcardio).


Follow-Up:
Providers on the case interpreted the ECG in Figure-1 as Brugada Phenocopy (ie, a BrugadaType-1 ECG pattern as a result



SUPERB REVIEWS 
 file:///Users/ekgpress/Downloads/fphys-15-1520008.pdf

https://www.jacc.org/doi/epdf/10.1016/j.jacep.2021.12.001


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Figure-2: XXXX


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Figure-3: XXXX




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Figure-4: XXXX


 

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Acknowledgment: My appreciation to Kianseng Ng (from Kluang, Johore, Malaysia) for making me aware of this case and allowing me to use this tracing.

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ADDENDUM (3/13/2026): 

I've included below selected material relating to Brugada ECG Patterns — beginning with a 2-part Video:

  • Although I recorded this 2-part ECG Video in 2021 ( = 5 years ago) — with the exception of a few changes in approach (that I highlight below) — this 2-part video remains current.
  • I introduced the concept of Brugada Phenocopy in my ECG Blog #238 (published in July, 2021). This distinction between Brugada ECG patterns arising from true Brugada Syndrome — vs those attributable to some other precipitating condition (ie, febrile illness; hyperkalemia; ischemia, etc.with resolution of the ECG pattern once the precipitating condition resolves — remains critical for risk assessment and management (Adytia and Sutanto — Current Prob in Card 49(6), 2024).


What's New?
I'll preface the 2-part Video below with select updates from the following excellent current references:

Consider the following:
  • XXXXXX

Figure-5: The 3 Brugada ECG Patterns (Adapted from Krahn et al — JACC: Clin Electrophys 8(3):386-405, 2022).








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In Part 1 of this ECG Video (9 minutes) — the essentials of Brugada Syndrome are reviewed.




Int Part 2 (8:00 minutes) — these essentials are applied clinically. 

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Figure-6: 2-page Summary of the essentials of Brugada Syndrome (from my ECG-2014-ePub).


 

Figure-7: World prevalence map of Brugada Syndrome. The overall worldwide prevalence of Brugada Syndrome is ~0.5/1,000 in the population. This prevalence is highest in Southeast Asia (at least 5 timesmore common than in North America). The country with highest prevalence of Brugada Syndrome is Thailand, with ~15 times higher prevalence thn the worldwide average. Brugada-2 patterns (ie, "Saddleback") are also much more prevalent in Southeast Asia than elsewhere in the world. (Excerpted from Vutthikraivit et al: Acta Cardiol Sin 34:267-277, 2018).


 

Figure-8: Summarizing Figure of KEY concepts reviewed in the above 2-part ECG Video.





Follow-Up:
Providers on the case interpreted the ECG in Figure-1 as Brugada Phenocopy (ie, a BrugadaType-1 ECG pattern as a result

My Reading of the ECG 

(1) V1, 2 are reminiscent of Brugada. There is a pseudo RBBB in V1. V1 has a rectilinear oblique descendent ST, followed by inverted symmetrical T wave. In V2 the ST is coved and it drops to a TWI. Strange! Two different ST Morphology, coved and rectilinear in the same ECG. In true Brugada, I would expect to see nearly identical changes in V1,2,3. 

(2) The ST segment coving and T inversion in V3, V4 is not generally what you see with a typical Brugada pattern. 

(3) There is also subtle-but-real ST coving in lead aVL.  

(4) The complexes in lateral leads V5-6, aVL and I are minute.

(5) Leads II, III, aVF are minute with unmistakable straightening of the ST in lead I.

(6) The Gestalt is that ongoing Ischemia is the dominant player in this ECG.

I called Dr CYY and asked if there was any other ECGs. Yes, there were two other ECGs, a second taken 14 minutes later and a third taken the next day.


14 minutes later, V1, V2 are still reminiscent of Brugada. Note subtle-but-real reduction in the ß-angle in lead V1 compared to ECG 1. The very sharp descent of the T waves in V3 V4 looks like am Wellens Type A. Is this an AMI that is in the process of spontaneous reperfusion and this is not a Brugada but a Brugada Phenotype?


V1 2 in the two previous ECGs were Ischemia induced Brugada Phenocopy, copy cats or mimicry! There is now reperfusion Deep TW which proves that V3, V4 in ECG 2 were inchoate Wellens Biphasic TW. Deep TW are seen in V2 3 4 and also in I and aVL. But the TW in II III aVF are now very de Winter in morphology, especially so in lead II and we did say earlier that “Leads II, III, aVF are minute with unmistakable straightening of the ST in lead I.” 


1 My first thought was that de Winter is a sign of LADA occlusion. However, Fabrizio Ricci et al stated that the pattern was described first in the left anterior descending coronary artery distribution, but it can occur in any coronary distribution.

2 We do know that de Winter can evolve into de Winter and vice versa.

3 Is it possible for Wellens and de Winter T-waves to be present in different arteries in the same patient, simultaneously? They represent different phases of the same pathological process. What we have here is Wellens and de Winter appearing at the same time but in different arteries, the first is reperfusing and the second is the process of occluding. 

5 Other thoughts. Classic descriptions of Wellens and de Winter are Wellens is “pain free” and de Winter is “pain filled.” All three ECGs here are pain free.

Unfortunately, we do not have any other 


Emeritus Professor Ken Grauer

Hi Kianseng. INTERESTING case! I agree with your interpretation. 1st ECG (11:37 am) — shows typical Brugada pattern in lead V1. But the ST segment coving and T inversion in V3, V4 is not generally what you see with a typical Brugada pattern (that most often has affected leads being V1,2,3 — and is not supposed to show ST coving …). There is also subtle-but-real ST coving in lead aVL in this 1st ECG.

2nd ECG (12:51pm) — Note subtle-but-real reduction in the ß-angle in lead V1 compared to ECG #1. The very sharp descent of the T in V3 (assuming there was no chest pain at this point) looks like a Wellens T wave … 

3rd ECG (Aug 7) — No more Brugada phenocopy. Instead, deep precordial T wave inversion consistent with reperfusion T waves (also in aVL) — so I agree completely with your interpretation!

:) Ken


Hi Kianseng (2/15/2026)

Kianseng Ng, Clinical Lecturer in Internal Medicine in Kluang, Johore, Malaysia.

 

Good to hear from. Great case that you have resurfaced. I think (but cannot completely remember) that the reason I did not publish this one was for lack of follow-up …

 

That said — the ECG patterns are so very suggestive — that it IS worth making an ECG Blog of this, even if you cannot get any follow-up!

 

So — LET ME KNOW:

  • Were Troponins ever done? (You said in the attached Word document that they may not have been … but please confirm if you have any information as to whether they were ever done?
  • Am I correct that this patient never received cardiac cath?
  • Do you know what happened to the patient? (Looks like there was acute MI with multi-vessel disease in LAD and RCA distribution — so just wondering if the patient survived).

 

In the past — I acknowledged you as per the attached. Do you want to add anyone else to the acknowledgment? Do you want to add the city in Malaysia?


Dear Emeritus Professor  Ken Grauer;

Wow, we are excited, very excited indeed. 

You asked 1 Were Troponins ever done? Sadly, no! The Physician in charge thought it was unnecessary 2 You are right, cardiac Cath was never done 3 Do you know what happened to the patient? No, we do not. The doctor who sent me the ECGs tried calling him but I believed he flew back to his home land. When You do publish this, could you add Kianseng Ng, Clinical Lecturer in Internal Medicine in Kluang, Johore, Malaysia. I teach in a private medical school (IMU) and the students are keen followers of your blog. Thank you and may God bless you and your family abundantly for your labour of love. Thank you sir, you made my day!

Warm Regards' — Kianseng



======================
ECG Blog #238 = What is Phenocopy?
https://ecg-interpretation.blogspot.com/2021/07/ecg-blog-238-53-what-is-phenocopy.html
======================

The ECG shown in Figure-1 was obtained from an elderly woman, who presented to the ED (Emergency Department) with an acute febrile illness (40°C).

  • How would you interpret her initial ECG?
  • Clinically — Could this be an early acute antero-septal STEMI?

 

Figure-1: ECG obtained from an elderly woman with an acute febrile illness (See text).


 

 

The Case Continues:

The ECG was repeated (Figure-2) — this time with anterior leads placed 1 interspace higher.

 

Figure-2: Repeat ECG of the tracing shown in Figure-1, with anterior leads placed 1 interspace higher (See text).

 

QUESTION:

  • Do these serial tracings suggest an acute evolving anterior STEMI?

 

 

 

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NOTE: Some readers may prefer at this point to refer to ECG Media PEARL #53 before reading My Thoughts regarding the ECGs in Figure-2. This 2-part ECG Video (9 minutes and 8 minutes) — reviews the ECG recognition and clinical significance of Brugada-1 and Brugada-2 ECG patterns + it clarifies the concept of Brugada Phenocopy.

  • For an excellent state-of-the-art Review article on Brugada Syndrome — CLICK HERE (Brugada J et al: J Am Coll Cardiol 72(9) 1046-1059, 2018).
  • For a Review on the entity of Brugada Phenocopy — CLICK HERE (Anselm D et al: World  Cardiol 6(3) 81-86-2014).
  • For a study documenting the inability of experts to distinguish between a Brugada-1 ECG pattern from Brugada Syndrome vs Brugada Phenocopy — CLICK HERE (Gottschalk et al: Europace 18, 1095-1100, 2016).
  • For brief summary of this material — Please refer to Figures-5-6 and -7 in the Addendum below.

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


My THOUGHTS on this Case:

Looking first at the ECG in Figure-1 — The rhythm is sinus — all intervals (PR, QRS, QTc) and the axis are normal — and there is no chamber enlargement.

 

Regarding Q-R-S-T Changes in Figure-1:

  • There are no Q waves.
  • R Wave Progression is normal, with transition (where the R wave becomes taller than the S wave is deepoccurring normally between leads V3-to-V4.
  • Regarding ST segments and T waves — the most striking abnormality is the ST elevation in leads V1V2 and V3, with "double-hump" upward concavity in lead V3.
  • ST segments are noticeably flattened in several limb leads — as well as in lateral chest leads (that also show slight ST depression).

 

My Impression of ECG #1: There is no denying the presence of anterior ST elevation with ST segment flattening and slight ST depression in other leads.

  • That said — Against these ST-T wave changes in ECG #1 representing an acute cardiac event — is the clinical history of acute febrile illness in this elderly woman, with no mention in the history of associated chest pain.

 

QUESTION:

What happened in ECG #2 (bottom tracing in Figure-2)?

 

 



ANSWER:

The main difference between ECG #1 and ECG #2 is the appearance of the ST-T waves in leads V1, V2 and V3:

  • The R' peak in leads V1 and V2 is higher in ECG #2, with sharp downsloping that leads into a more noticeably inverted T wave.
  • The "double-hump" upward ST segment concavity that was seen in lead V2 of ECG #1 — is now seen in lead V3 of ECG #2.

 

My Impression of ECG #2: The ECG picture in Figure-2 stongly suggests we are seeing Brugada ECG patterns.

  • The "double-hump" upward ST segment concavity in lead V2 of ECG #1 — is consistent with a Brugada-2 (ie, "Saddleback" ) pattern.
  • The higher-rising, steeper downsloping ST-T wave appearance in leads V1 and V2 of ECG #2 — now meets criteria for a Brugada-1 ECG pattern, with a Brugada-2 pattern now seen in lead V3.
  • In view of the clinical history — this is unlikely to represent an acute anteroseptal STEMI.

 

PEARL #1: It turns out that ECG #2 was repeated soon after ECG #1. This illustrates how the simple measure of placing anterior leads 1 or 2 interspaces higher on the chest may serve to bring out a Brugada ECG pattern!

 

 

The Case Continues:

The patient was treated for her acute febrile illness. Her ECG was repeated after her fever had resolved (Figure-3).


Figure-3: Repeat ECG following resolution of this patient's fever — compared to the initial ECG in this case (See text).

 

QUESTION:

Does the patient in today's case have Brugada Syndrome?

 

 

 

WHAT is Brugada Syndrome?

First described in 1992 — the Brugada Syndrome is important to recognize because of an associated very high risk of sudden death in otherwise healthy young or middle-aged adults who have structurally normal hearts.

  • The prevalence of Brugada Syndrome in the general population is ~1/2,000. The syndrome has become a leading cause of sudden death in young adults (under 40 years of age).
  • PEARL #2: Brugada Syndrome is much more common in Southeast Asia compared to the rest of the world. When considering the possibility of this syndrome — demographics of the patient are important! (See Figure-6 in the Addendum below).
  • PEARL #3: Although the genetics of Brugada Syndrome are complicated — the gender of the patient is also important. There is a distinct male predominance to this syndrome.


Personal Reflection: I never learned about Brugada Syndrome in medical school (the syndrome had not yet been described). But especially during the past 10 years, in which I've closely followed numerous international ECG internet forums — I've seen countless cases, especially of transient Brugada ECG patterns similar to today's case. 

  • Once a clinical entity is "discovered" — it begins to get noticed with increasing frequency.

 

 

Regarding BRUGADA Syndrome vs Phenocopy: 

I reference an excellent state-of-the-art Review article on Brugada Syndrome (Brugada J et al: J Am Coll Cardiol 72(9) 1046-1059, 2018). I've synthesized key aspects of this article:

  • Brugada Type-1 ECG pattern is diagnosed by the finding of ST elevation of ≥2 mm in one or more of the right precordial leads (ie, V1, V2, V3) — followed by an r’ wave and a coved or straight ST segment — in which the ST segment crosses the isoelectric line and ends in a negative T wave (See Panel A in Figure-4).
  • A Brugada-1 pattern may either be observed spontaneously (with leads V1 and/or V2 positioned normally — or — positioned 1 or 2 interspaces higher than usual) — or — a Brugada-1 pattern may be observed as a response to provocative drug testing after IV administration of a sodium-channel blocking agent such as ajmaline, flecainide or procainamide.
  • NOTE: In the past, the diagnosis of Brugada Syndrome required not only the presence of a Brugada-1 ECG pattern — but also a history of sudden death, sustained VT, non-vasovagal syncope or a positive family history of sudden death at an early age. This definition was changed following an expert consensus panel in 2013 — so that at the present time, all that is needed to diagnose Brugada Syndrome is a spontaneous or induced Brugada-1 ECG pattern (without need for additional criteria).
  • Panel B in Figure-2 illustrates the Brugada Type-2 or "Saddleback" ECG pattern. This pattern may be suggestive — but by itself, it is not diagnostic of Brugada Syndrome (See Figure-4).


 

Figure-4: Review of ECG Patterns in Brugada Syndrome (adapted from the above cited article by Brugada et al in JACC: Vol 72, Issue 9) — (A) Brugada-1 ECG pattern, showing coved ST-segment elevation ≥2 mm in ≥1 right precordial lead, followed by a negative T-wave. (B) Brugada-2 ECG pattern (the “Saddleback” pattern) — showing concave-up ST-segment elevation ≥0.5 mm (generally ≥2 mm) in ≥1 right precordial lead, followed by a positive T-wave. (C) Additional criteria for diagnosis of a Brugada-2 ECG pattern (TOPthe ß-angleBOTTOMA Brugada-2 pattern is present if 5 mm down from the maximum R’ rise point — the base of the triangle formed is ≥4 mm — as this ensures a ß-angle ≥58°).


 

PEARL #4: A number of conditions other than Brugada Syndrome may temporarily produce a Brugada-1 ECG pattern. A partial list includes the following:

  • Certain drugs (antiarrhythmics; calcium channel blockers; ß-blockers; antianginals; psychotropic medications; alcohol; cocaine; other drugs).
  • Acute febrile illness.
  • Variations in autonomic tone.
  • Hypothermia.
  • Electrolyte imbalance (hypokalemia; hyperkalemia).
  • Ischemia/infarction.
  • Cardioversion/defibrillation.
  • Bradycardia.

 

KEY Point: Development of a Brugada-1 or Brugada-2 ECG pattern as a result of one or more of the above factors — with resolution of this Brugada ECG pattern after correction of the precipitating factor(s) is known as Brugada Phenocopy.

  • The importance of being aware of this phenomenon of Brugada Phenocopy — is that correction of the underlying condition (ie, the acute febrile illness in today’s case) may result in resolution of the Brugada-1 ECG pattern — with a much better longterm prognosis compared to patients with true Brugada Syndrome (ie, an ICD may not be needed, as it probably would be if true Brugada Syndrome was present!).
  • NOTE: To ensure a diagnosis of Brugada Phenocopy — the patient should have: i) A negative family history of sudden death; ii) Lack of a Brugada-1 ECG pattern in 1st-degree relatives; iii) No history of syncope, serous arrhythmias, seizures or nocturnal agonal respiration; andiv) A negative sodium channel-blocker challenge test.

 

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Final Comment on Today's Case:

Assuming the elderly woman in today's case had otherwise been healthy (without a personal history of syncope, serious arrhythmias, seizures or nocturnal agonal respiration) — the fact that the Brugada-1 ECG pattern we initially saw completely resolved so soon after fever resolution, strongly suggests she has Brugada Phenocopy (and not Brugada Syndrome) — and that her longterm prognosis is likely to be good.

  • Whether she needs to undergo a negative sodium channel-blocker challenge test at her advanced age (and what impact her family history might have at her age) — are issues for her informed consent and medical providers to decide.

 


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Acknowledgment: My appreciation to 유영준 (from Seoul, Korea) for making me aware of this case and allowing me to use this tracing.

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References & Related ECG Blog Posts to Today’s Case: 

  • For an excellent state-of-the-art Review article on Brugada Syndrome — CLICK HERE (Brugada J et al: J Am Coll Cardiol 72(9) 1046-1059, 2018). 
  • For a Review on the entity of Brugada Phenocopy — CLICK HERE (Anselm D et al: World  Cardiol 6(3) 81-86-2014).
  • For a study documenting the inability of experts to distinguish between a Brugada-1 ECG pattern from Brugada Syndrome vs Brugada Phenocopy — CLICK HERE (Gottschalk et al: Europace 18, 1095-1100, 2016).

  • ECG Blog #50 — For a case of Brugada Syndrome.

  • The September 5, 2020 post in Dr. Smith's ECG Blog (Please scroll down to the bottom of the page to see My Comment). This case shows an example of Brugada Phenocopy as a result of Hyperkalemia
  • The May 6, 2019 post in Dr. Smith's ECG Blog (Please scroll down to the bottom of the page to seeMy Comment). This case reviews an example in which it was difficult to distinguish between Brugada Phenocopy vs an ongoing acute STEMI
  • The September 8, 2019 post in Dr. Smith's ECG Blog (Please scroll down to the bottom of the page to see My Comment). This case reviews another example of Brugada Phenocopy as a result of Hyperkalemia.

 

 



Thursday, February 26, 2026

EXTRA COPY — ECG Blog #520 — How Certain Are You? - EXTRA


You are asked to interpret the ECG in Figure-1. Which of the following choices provides the best answer?
  • A) AFib with a rapid ventricular response.
  • B) SVT with RBBB aberration.
  • C) The rhythm could be VT.
  • D) The rhythm is VT.

Figure-1: Which of the above choices is the best answer? 
= = = = = = =
[ Abbreviations: AFib (Atrial Fibrillation) — 
SVT (SupraVentricular Tachycardia) — RBBB (Right Bundle Branch Block) — VT (Ventricular Tachycardia)].

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

MY Approach to Today's Tracing:
As much as we always want at least a brief history (including at least the age of the patient — and the reason why the ECG was recorded) — we are not provided with one. Nevertheless, there is enough information to select the right answer.
  • Take another LOOK at today's tracing in Figure-2. For clarity — I've numbered the beats in the long lead II rhythm strip.

Figure-2: I've numbered the beats in today's tracing.

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

MY Thoughts:
By the P's, Q's, 3R Approach (See ECG Blog #185) — the rhythm in Figure-2 is a regular WCT (Wide-Complex Tachycardia):
  • The overall rhythm appears to be Regular. This is best assessed in simultaneously recorded leads I and III, in which it is easier to see the consistency in the R-R interval (and more difficult to appreciate in lead II — where there is more artifact distortion).
  • The Rate of the rhythm is slightly more than 150/minute (ie, with an R-R interval of slightly less than 2 large boxes in duration).
  • The QRS is wide (at least 3 small boxes in duration — therefore ≥0.12 second).

  • Are there P waves?

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

What Can We Already Rule Out?
  • The fact that the R-R interval in Figure-2 is regular effectively rules out AFib (and if we can confirm that P waves are truly present — this would definitively rule out AFib).

What We Know:
  • The rhythm in Figure-2 is a regular WCT (Wide Complex Tachycardia).
  • The rate of the rhythm is slightly more than 150/minute
  • There is no clear sign of sinus P waves (ie, There is no consistent upright P wave with constant PR interval preceding each QRS complex in the long lead II rhythm strip).
  • The above said — a number of small upright deflections in the baseline do appear to be present throughout the long lead II. These could be P waves.
  • PEARL #1: Assuming today's patient is an adult — by far, the most common cause of a regular WCT rhythm without clear sign of sinus P waves is VT. Therefore — We need to assume VT until proven otherwise!

PEARL #2:
 We can go 1 step further in our differential diagnosis by looking at QRS morphology
  • Although the predominantly upright QRS complex in lead V1, in association with wide terminal S waves in lateral lead V6 could be consistent with RBBB conduction — you should virtually never see an all negative QRS complex in lead I with a supraventricular rhythm
  • Based on QRS morphology then — this strongly suggests that the rhythm in Figure-2 is VT (which means we can effectively rule out SVT with RBBB aberration)

QUESTION:
  • But — Are we 100% certain that today's rhythm is VT?


My Next Thoughts:
At this point in my interpretation — I would estimate the statistical likelihood that the rhythm in today’s case is VT at over 95%! (based on the fact that sinus P waves are absent in this regular WCT rhythm — and the finding that QRS morphology in lead I is all negative). That said — I prefer to increase the accuracy of my interpreatation as much as possible — and — there is a way we can increase this statistical likelihood to 100%
  • To Emphasize: IF we were at the bedside with this patient — the 1st thing we would do is determine if the patient is hemodynamically stable! That's because if the patient is not stable with this rhythm — then it would no longer matter what the rhythm is, because synchronized cardioversion would then be immediately indicated.
  • But assuming that this patient is hemodynamically stable — we would then have a moment in time to quickly look a little closer.

  • Please NOTE: I have described my above thoughts in slow motion. With practice and experience — You should be able to arrive at this point in the process in no more than 10-to-15 seconds!

The Next Step: So — Are there P waves in Today’s ECG?
Take another LOOK at the ECG in Figure-2.
  • Is there an EASY way to determine with certainty whether P waves are (or are not) present in today’s ECG?



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

ANSWER: Are there P waves in Today’s ECG?
The KEY to optimizing the accuracy of our interpretation — is to determine IF underlying regular sinus P waves are present!
  • PEARL #3: As I have often emphasized in this ECG Blog — the simple step of labeling P waves is incredibly helpful for determining the presence and nature of underlying atrial activity.
  • In Figure-3 — I’ve labeled with RED arrows those small upright deflections in the long lead II rhythm strip that look like they may represent P waves.
  • If these RED arrows in Figure-3 are in fact highlighting the presence of underlying P waves — Does this suggest what the P-P interval might be?

  • PEARL #4: If we can demonstrate that the small upright deflections in Figure-3 remain consistently regular throughout the long lead II — this would prove that these small upright deflections do represent an underlying rhythm of regular P waves. 
  • To do this — I look to see what the shortest distance between 2 consecutive RED arrows might be. Doesn't it look like this shortest distance repeats between the 4th and 5th RED arrows — and between the 7th and 8th RED arrows?

Figure-3: I've highlighted with RED arrows the small upright deflections in the long lead II rhythm strip that I can clearly see.


PEARL #5: To determine within seconds if an underlying rhythm of regular P waves may be present in the long lead II — You have to use calipers!
  • To Emphasize: I am not encouraging the use of calipers if your patient is unstable. A hemodynamically unstable patient in a WCT rhythm should be immediately cardioverted!
  • But IF the patient whose rhythm is shown in Figure-3 is hemodynamically stable — it takes no more than seconds to walk out the rhythm that I've highlighted with colored arrows in Figure-4.

Figure-4: I've added WHITE and PINK arrows to Figure-3.


Breaking Down Figure-4: 
All that I've done to get from Figure-3 to Figure-4 — is to set my calipers to the P-P interval suggested by the distance between the 4th and 5th RED arrows in Figure-4 (which equals the distance between the 7th and 8th RED arrows) — and then to "walk out" this presumed P-P interval with your calipers throughout the remainder of the long lead II.
  • Although on-time regular wide QRS complexes prevent us from seeing P waves under the WHITE arrows that I've added to Figure-4 — a definite underlying upright deflection can be seen under each of the 2 PINK arrows!
  • This tells us that the colored arrows in Figure-4 represent an underlying rhythm of regular P waves occurring at an atrial rate of ~90/minute!

PEARL #6:
 Since the P waves represented by the colored arrows in Figure-4 are completely unrelated to neighboring QRS complexes — this tells us there is AV dissociation throughout the long lead II rhythm strip. The finding of AV dissociation within a regular WCT rhythm proves that the rhythm is VT!
  • In my experience — AV dissociation is greatly overdiagnosed! This is because of the tendency to assume there is AV dissociation whenever clinicians see any suggestion of underlying baseline deflections. In my decades of following up on regular WCT rhythms — most cases of WCT rhythms labeled as showing "AV dissociation" do not truly represent this finding.
  • It is because true AV dissociation proves that a WCT rhythm is VT — that I feel it best to avoid the diagnosis of AV dissociation unless you can clearly demonstrate the presence of underlying regular P waves throughout a significant portion of the rhythm. Doing so can only be done by use of calipers.
  • Unfortunately — the clinical reality is that it is rare to see AV dissociation in faster WCT rhythms. This is because when a WCT occurs at a faster rate — the wide QRS complexes and often large-sized ST-T waves are highly efficient at "hiding" underlying P waves.

  • BOTTOM Line: The colored arrows in Figure-4 do demonstrate AV dissociation. This proves beyond doubt that today's WCT rhythm is VT!
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NOTE: For readers wanting more regarding the concepts and clinical utility of AV dissociation in assessing a regular WCT rhythm — Review of ECG Blog #335 may prove insightful.
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Today's CASE Continues:
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Figure-5: XXX


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Figure-6: XXX


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Figure-7: XXX


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Acknowledgment: My appreciation to Konstantin Тихонов (from Moscow, Russia) for the case and this tracing.
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ADDENDUM (2/XXX/2026):

I refer the reader to my ECG Blog #196 — in which I walk through a similar problem-solving process for another regular WCT rhythm. 

  • I've excerpted from that post my Audio PEARL on assessing the regular WCT — as well as Figures on my "3 Simple Rules" and on QRS morphology in lead V1.


ECG Media PEARL #13a (12:20 minutes Audio) — reviews “My Take” on assessing the regular WCT (Wide-Complex Tachycardia), when sinus P waves are absent — with tips for distinguishing between VT vs SVT with either preexisting BBB or aberrant conduction.




Figure-8: Use of the “3 Simple Rules” for distinction between SVT vs VT (excerpted from my ACLS-2013-ePub).




Figure-9: Use of lead V1 for assessing QRS morphology during a WCT rhythm (excerpted from my ACLS-2013-ePub).



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Константин Тихонов <dropattack03@icloud.com>  (2/11/2026)

I just can't seem to fully explain a certain point to myself

I had a patient on call today. This is a 45-year-old man with a history of hypertrophic cardiomyopathy (without obstruction of the outflow tract of the left ventricle) and thyrotoxicosis. In January of this year, he had two similar episodes, and he was hospitalized twice by an ambulance team. Both times, the rhythm was restored with the help of electric pulse therapy. The diagnosis was ventricular tachycardia. He called an ambulance for a rapid heartbeat. During our examination, the patient was not pale, and there was no diaphoresis. His blood pressure was 125/70, compared to his normal blood pressure of 130/80. His oxygen saturation was 97%. His respiratory rate was 16.

 

 ECG No. 1 was recorded first. After that, there was a short episode of sinus rhythm recovery with premature ventricular complexes, after which the tachycardia with wide QRS complexes recurred (ECG No. 2).


ECG No. 3 was recorded after 150 mg of amiodarone, after which the patient felt a significant improvement in his well-being.

 

My opinion:

I believe that ECG No. 1 shows ventricular tachycardia.

 

1. There is an almost regular rhythm with small differences in RR intervals in some places. (Black lines)

2. The electrical axis on ECG No. 1, in my opinion, is approximately +120 degrees, while on ECG No. 3 it is about +60 degrees.

3. I have marked with red arrows on ECG No. 1 the possible presence of atrioventricular dissociation, which I believe is present.

4. The R nadir time in lead II is more than 50 ms.

5. The QRS complexes in tachycardia are similar in morphology to the premature ventricular complexes on ECG No. 3.

 

 ECG No. 3 raises special questions. It seems to me that there are regular P waves, the first of which are conducted, while the second are not and are hidden in the ST-T of the ventricular extrasystoles. These P waves are very similar in morphology to the sinus waves, as can be seen by comparing their morphology, which I have indicated with blue arrows on ECG No. 3. Also, these possible P's are not premature, so they are probably not blocked atrial extrasystoles. Is it possible that after a sinus contraction, a ventricular extrasystole occurs that retrogradely depolarizes the AV node, but the next sinus P finds the AV node in the absolute refractory period and is not conducted to the ventricles?


MY REPLY:

Hi Konstantin.Yes — VERY interesting case. I would like to do an ECG Blog on this case. Because the tracings are so long, I will need to reduce them — and I probably will only show the 1st and 3rd tracings together with the laddergram that I’ve drawn below. If OK by you — I will acknowledge  you — and I’ll let you know when I publish this (it may be a little while — as I have other cases to go before this).

 

MUCH better to show this tracing when you ask the question about retrograde P waves — because I can now directly refer to this ECG.

  • There are NO retrograde P waves. You did a GREAT job highlighting the P waves. There is often some underlying sinus arrhythmia — which is the reason for slight change in P-P intervals.
  • You PROVE beyond doubt (100%) that this rhytm is VT. Assuming no lead misplacement — you virtually NEVER see an all negative QRS in lead I.
  • You very nicely highlight the on-time sinus P waves. This establishes AV dissociation, which especially given the abnormal QRS morphology tells us 100% that this rhythm is VT.
  • Your ECG #3 shows ventricular bigeminy. The attached laddergram shows what is happening = on-time sinus P waves that are unable to conduct because the ventricular beats do conduct retrograde and therefore prevent every-other on-time P wave from being conducted down to the ventricles.
  • This is a NICE PEARL — the fact that on-time sinus P waves continue throughout the tracing proves that beats #2,4,6,8,10,12 can not possibly be supraventricular (because if they were supraventricular, they would have reset the SA node)

 

I hope this makes sense. You did a GREAT job mapping out the P waves and the AV dissociation — and this PROVES this rhythm is VT. 

 

Do you have any more follow-up on this patient!

 

Take care.

 

: )  Ken

 

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KONSTANTIN Reply:

Thanks a lot, Ken. I am very glad that my version turned out to be correct, because I am now trying to learn to understand complex rhythms in more detail. 

 

On account of this patient. Later that night, the patient called an ambulance twice more and had two more recurrences of ventricular tachycardia. As a result, he was admitted to the hospital. He has been assigned to conduct an electrophysiological examination and the issue of installing a cardioverter-defibrillator will be considered.