Saturday, March 14, 2026

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


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).


CASE Follow-Up:
Providers on the case interpreted the ECG in Figure-1 as consistent with Brugada Phenocopy (ie, a BrugadaType-1 ECG pattern as a result of "something else" — but not a true Brugada Syndrome).
  • Because providers were certain ECG #1 was a manifestation of Brugada Phenocopy — serum Troponin was not ordered.

QUESTION: 
  • Do you agree with the above approach?

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NOTE: I review Brugada ECG Patterns in the ADDENDUM below:
  • A summary of Brugada Syndrome vs Phenocopy appears in Figure-6 — with more depth exploration in the 2-part ECG Video below (Total view time ~17 minutes).
  • For more of an update on Brugada Syndrome — See below!
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MY Thoughts on the CASE:
As is often the case — today's History is KEY ==> a middle-aged man who presents with new CP — but who was asymptomatic by the time today's initial ECG was recorded.

My interpretation of the ECG in Figure-1:
  • The rhythm is sinus.
  • The QRST complex in lead V1 (within the RED rectangle in Figure-2) — is diagnostic of a Brugada-1 ECG pattern.
  • That said — the shape of the ST segment coving in neighboring leads V2,V3,V4 differs from the very steep downsloping ST segment seen in lead V1.  
  • Deep, symmetric T wave inversion persists in leads V3 and V4.
  • More subtle ST-T wave changes are seen in the limb leads (ST segment straightening in leads I,II,III,aVF — and ST segment coving with slight elevation and T wave inversion in lead aVL). Given small size of the QRS in the limb leads (especially tiny in leads III and aVL) — these changes are subtle indeed!

  • BOTTOM Line for Figure-2: Although the QRST complex in lead V1 is typical for a Brugada-1 ECG pattern — the other findings described above are not expected with Brugada Phenocopy in the absence of ongoing ischemia. Instead, in this patient who presents for new-onset CP — We have to suspect that in addition to the typical Brugada-1 ECG pattern that we see in lead V1 — the neighboring chest leads also suggest there may be an ongoing acute infarction!

Figure-2: I've labeled KEY findings in ECG #1 (and added an insert with illustration of Brugada-1 and Brugada-2 ECG patterns).


The CASE Continues:
As noted above — serum Troponins were not obtained because the provider attributed all ECG findings in Figure-2 to Brugada "Phenocopy".
  • A short while later — the ECG in Figure-3 was recorded. 

HINT: The changes in the chest leads of ECG #2 are extremely subtle.
  • Do you see them?

Figure-3: Repeat ECG done a short while after ECG #1.


Comparison of the ECGs in Figure-3:
As noted above — the changes between the 2 ECGs in Figure-3 are extremely subtle:
  • The R' that was seen in ECG #1 has thinned out — with subtle-but-real reduction in the ß-angle in ECG #2 (See the insert in the upper right of Figure-2 regarding calculation of the ß-angle).
  • In neighboring leads V2,V3,V4 of ECG #2 — the ST segment coving is less pronounced, and there is narrowing with slight reduction in the depth of T wave inversion that was seen in the initial ECG.
  • Bottom Line: Although subtle indeed — ECG #2 suggests ongoing evolution of reperfusion T waves.

================================== 

Figure-4 shows the final ECG done the next day ( = ECG #3):
  • Unfortunately — I lack details on this case beyond knowing that the patient had no more chest pain — that Troponins were never done — and that there was no cardiac catheterization.

QUESTION:
  • How would you explain the ECG changes seen in Figure-4?

Figure-4: Comparison between the initial and the final ECGs that were recorded in today's case. How best to explain these changes?


MY Thoughts on the ECGs in Figure-4:
Whereas the changes in Figure-3 (between ECGs #1 and #2) were extremely subtle — the changes now seen in Figure-4 (between ECGs #1 and the final ECG #3) are obvious.
  • The Brugada-1 ECG pattern in lead V1 of ECG #1 has now almost completely resolved in ECG #3.
  • ST segment coving without ST elevation persists in neighboring chest leads of ECG #3 — with marked deepening of symmetric T wave inversion.
  • In the limb leads of ECG #3 — there has been slight axis shift, with marked increase in the now widened and tall inferior T waves (essentially the reciprocal opposite ST-T wave picture that is now seen for leads V2 and V3 in ECG #3).
  • Deep, widened T wave inversion is now seen in leads I and aVL of ECG #3.
  • Bottom Line: Even without Troponin values and without cardiac catheterization — the ECG evolution that is now obvious in ECG #3 confirms reperfusion changes following extensive infero-antero MI (presumably following acute LAD occlusion in a patient with multi-vessel disease).

================================== 

Final Editorial NOTE:
I initially hesitated using today's case because I lacked follow-up. Efforts to contact today's patient were unsuccessful. He lived remotely, away from health care facilities — and apparently flew back to the island where he lived without returning calls.
  • Today's case is insightful — because it illustrates that among the causes of a transient Brugada-1 ECG pattern are acute LAD occlusion, which may superimpose on the ST-T wave changes of acute infarction.
  • In my experience — the most common precipitants of a Brugada-1 ECG pattern in patients who do not have Brugada Syndrome (ie, Brugada "Phenocopy" ) — are acute febrile illness and hyperkalemia. I've seen cases in which there is complete resolution of the Brugada-1 ECG pattern after resolution of the febrile illness and hyperkalemia.
  • But — acute ischemia and/or infarction and/or S/P cardiac arrest may also be causes of a Brugada-1 ECG pattern, as was seen in today's patient whose presenting complaint was new chest pain.
 

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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 added below material relating to Brugada ECG Patterns — beginning with my 2-part ECG Video:

  • NOTE: 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, and hopefully facilitates recall of Brugada ECG patterns.
  • I introduced the concept of Brugada Phenocopy in my ECG Blog #238 (published in July, 2021). This distinction between true Brugada Syndrome — vs a transient Brugada ECG pattern attributable to some other precipitating condition (ie, febrile illness; hyperkalemia; acute ischemia/MI, etc.with resolution of the ECG pattern once the precipitating condition resolves — remains critical for risk assessment, as well as for optimal 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 comprehensive newer references:

Brugada ECG Patterns: 
  • As per the above JACC Review — for practical purposes, the only ECG pattern that is diagnostic of BrS (Brugada Syndrome) is Type-1 (as shown below for A in Figure-5 — when this ECG pattern is present in ≥1 of the anterior leads = V1,V2,V3).
  • I had not been distinguishing between a Type-2 vs Type-3 pattern (as per my illustration in Figure-2 above). For investigators who do favor distinction between Type-2 ( = B in Figure-5) and Type-3 ( = C in Figure-5) — the shape of the ST-T wave is similar, with the difference being that with Type-3, there is <2mm of ST elevation. 
  • My Preference: I still favor use of only 2 Types ( = Brugada Types-1 and -2) — but whatever your preference, it’s good to be aware that some investigators employ the use of 3 Types (as shown below in Figure-5).
  • Neither Type-2 nor Type-3 Brugada ECG patterns alone are diagnostic of BrS. That said — BrS can be diagnosed in these patients IF provocative testing with a SCB (Sodium Channel Blocker) converts a Type-2 or Type-3 pattern into a Brugada-1 ECG. 

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


Additional Considerations:
The KEY to optimal management of BrS lies with Risk Assessment (To Emphasize: Risk assessment is best performed by cardiologists well versed in the many manifestations of BrS — with current accepted concepts explored in the above 2 references).
  • SAEs (Serious Arrhythmic Events) — are rarely the 1st symptom in patients with BrS (which emphasizes the importance of identifying Brugada ECG Patterns — and determining which of these patients are at highest risk for SAEs, and therefore in need of preventive treatment).
  • Aside from a malignant arrhythmia — highest risk of SAEs are in: i) Patients with a history of cardiogenic syncope; — ii) The presence of a spontaneous Brugada-1 ECG; — and/oriii) Association with Other Factors (ie, Excessive alcohol consumption — hypo-/hyperKalemia — Acidosis — Febrile Illness — have all been shown to facilitate Brugada-1-induced SAEs).

  • The sensitivity for ECG recognition of a Brugada-1 pattern is increased by ~50% including high-lead positions (ie, Recording of leads V1 and V2 not only in the 4th IC space — but also in the 2nd and 3rd IC spaces, so as to account for anatomic variation in the position of the vulnerable RV Outflow Track).
  • Be aware of intermittent, spontaneous fluctuations in the presence and potential sudden resolution of a Brugada-1 ECG pattern, especially in response to potential precipitating factors such as febrile illness, hyperkalemia, and/or certain drugs. As a result — Provocative Testing with a SCB (Sodium-Channel Blocking agent), is an important adjunct in risk assessment of the patient with a Brugada-1 ECG pattern (NOTE: Not all SCBs used in provocative testing are created equal — but this concept extends well beyond the scope of this ECG Blog).
  • Genetic Testing is an important part of Brugada-1 risk assessment (especially since such testing may facilitate identifying family members at risk).

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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. 

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

 

 

Figure-6: 2-page Summary of the essentials of Brugada Syndrome (from Grauer K: ECG-2014-ePub, KG/EKG Press, 2014).



 

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 times more common than in North America). The country with highest prevalence of Brugada Syndrome is Thailand, with ~15 times higher prevalence than for 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: Summary of KEY concepts reviewed in the above ECG Video.




 




 



 



Saturday, March 7, 2026

ECG Blog #521 — Inferior MI? — Anything else?


The ECG in Figure-1 was obtained from a middle-aged man with a long history of smoking — who presents with severe new-onset CP (Chest Pain).
  • The patient reports having 2 episodes of severe CP — each of which spontaneously resolved. He then presented to the ED (Emergency Department) several hours after the 2nd episode (ie, He was not having CP at the time ECG #1 was recorded).
  • The initial Troponin level was negative for acute infarction.

QUESTIONS
  • How would you interpret the ECG in Figure-1?
    • Should you activate the cath lab?

Figure-1: The initial ECG in today's case — obtained from a middle-aged man with CP — but who was asymptomatic at the time this ECG was recorded. (To improve visualization — I've digitized the original ECG using PMcardio).



MY Thoughts on Today's ECG:
The ECG in Figure-1 shows a regular sinus rhythm at ~80/minute. Intervals (PR, QRS, QTc) and the axis are normal. There is no chamber enlargement.

Regarding Q-R-S-T Changes:
  • Q Waves: There are q waves in the lateral leads (ie, leads I,aVL; and leads V4,V5,V6). These have the appearance of normal septal q waves — in that all of these q waves are narrow and small in size.
  • R Wave Progression: Normal (ie, R wave amplitude progessively increases as we move across the chest leads — with transition occurring normally between leads V2-to-V4).

Regarding ST-T Wave Changes:
  • In this patient with new CP — My "eye" was immediately drawn to the "scooped" ST depression in lead V2 (within the RED rectangle in Figure-2)
  • This ST depression continues in neighboring leads V3,V4 (RED arrows in these chest leads— but has largely resolved by lead V5.

  • ST-T wave changes in the inferior leads are more difficult to evaluate (See below).


Figure-2: I've labeled the ECG in today's case.

==========================
ANSWERS: Putting It All Together . . .
There are a number of reasons why assessment of today's case is challenging. Unfortunately, we lack many details and only have limited follow-up. That said, my purpose in presenting this case — is that the following points can still be made from the brief history we are given, and from today's initial ECG:
  • The history of several episodes of new-onset and severe CP in this middle-aged man with a longterm history of smoking immediately place him in a higher-risk group for having an acute cardiac event. Awareness of this clinical situation should lower our threshold for accepting ST-T wave findings as abnormal.
  • Availability of a prior ECG for comparison would have made it much easier to determine if the ST-T wave changes that we see in ECG #1 are acute.
  • Repeating the ECG within 10-20 minutes of the initial tracing is advisable when symptoms are new and there is uncertainty about whether ST-T wave findings are acute — as diagnostic "dynamic" ST-T wave changes may sometimes be seen within minutes (See ECG Blog #115 — and ECG Blog #459)
  • Obtaining a bedside Echo may sometimes be diagnostic if it shows a localized wall motion abnormality. (While Echo may be diagnostic if positive — a normal Echo does not rule out an acute event if the patient is not having CP at the time the Echo is done).
  • The initial normal hs-Troponin in today's case in no way rules out an acute cardiac event (See ECG Blog #508). In addition to infarct size, whether or not Troponin will be elevated depends on how long the "culprit" artery is occluded for — which we do not know in today's case. But if the duration of time that the "culprit" artery is occluded is very brief — there may not be any Troponin elevation at all (and on occasion — the first 2 Troponin values may come back normal despite the patient going on to develop a STEMI).

Consider the following additional points:
  • The patient was not having CP at the time ECG #1 was recorded. This suggests that spontaneous resolution of acute coronary occlusion may have occurred — in which case acute ST-T wave abnormalities that were present during CP may signficantly improve (and even resolve).
  • That said — there normally should be slight, gently upsloping ST elevation in leads V2 and V3. This is why in a patient with new CP — the finding of ST depression that is maximal in leads V2,V3,V4 (as is seen in ECG #1) — is diagnostic of acute posterior MI until proven otherwise! (See ECG Blog #351 — and ECG Blog #298, among many others).
  • NOTE: Because of a common blood supply to the inferior and posterior walls of the left ventricle — I always look for acute inferior lead changes whenever I suspect acute posterior OMI. Unfortunately, the inconsistent ST-T wave appearance in the inferior leads of ECG #1 makes it all-but-impossible to assess the inferior leads (ie, Whereas complex B within the BLUE rectangle suggests a straightened, hyperacute ST segment with terminal T wave inversion — complexes A and C do not look acute).

BOTTOM Line:
 Maximal ST depression in leads V2,V3,V4 in this patient with a history of new CP suggests acute posterior OMI until proven otherwise. Knowing that this patient's CP had completely resolved at the time ECG #1 was recorded may account for relatively modest ST-T wave changes in the remaining leads.
  • Ideally — the cath lab would be activated on seeing ECG #1.
  • If the interventionist was reluctant to catheterize the patient at this point — then the following actions might serve to expedite acceptance to perform this procedure: i) Repeating the ECG within 10-20 minutes — and if this initial repeat tracing failed to show dynamic changes — follow-up with a few more repeat tracings within the hour; — ii) Immediately repeating the ECG if at any time the patient's CP returns; — iii) Searching for a prior ECG on this patient (that most probably would confirm that the ST depression in leads V2,V3,V4 is acute); — iv) Performing bedside Echo, looking for a localized wall motion abnormality; — and, v) Looking for any elevation in the 2nd Troponin value (which in a patient with new worrisome symptoms is indication for prompt cath — even when ECG changes are less than diagnostic).
==========================

CASE Follow-Up: 
My follow-up is limited — but the results that I have reinforce the above clinical points:
  • The repeat Troponin was elevated at ~60 (I'm not sure of units or norms — but a value of 60 is clearly elevated).
  • A repeat ECG done many hours later seemed to show less acute changes compared to ECG #1.
  • Bedside Echo done the next day showed a wall motion abnormality localized to lateral and posterolateral segments.
  • Cardiac cath done the next day confirmed the LCx (Left Circumflex) as the "culprit" artery (I do not know about additional cardiac cath findings).

Lessons to Be Learned:
  • Waiting for ST elevation before activating the cath lab misses a substantial percentage of acute coronary occlusions. Acute posterior OMI is most easily recognized in a patient with new CP by maximal ST depression in leads V2,V3,V4 — which is much easier to recognize and more reliable than than trying to assess the dampened amplitudes obtained with posterior leads (See ECG Blog #80). Posterior OMI is the best example of how we can make a presumptive diagnosis of acute coronary occlusion without insisting on ST elevation
  • The diagnosis of acute OMI could have been made significantly earlier in today's case.
  • Delay in diagnosis (and therefore in reperfusion treatment of acute coronary occlusion) comes at a price. The most benefit from reperfusion occurs within the first 4 hours after acute coronary occlusion (Every 2-hour delay results in 60% more myocardium infarcted). Documentation of these Lessons-to-be-Learned is forthcoming in these 3 posts from Dr. Smith's ECG Blog ( = the February 8, 2026 post — the January 15, 2026 post — and the October 23, 2025 post with My Comment appearing at the bottom of the page in each of these posts).

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Acknowledgment: My appreciation to Hisham Alshamekh (from Egypt) for the case and this tracing.
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ADDENDUM (3/7/2026)
For more regarding the concept and ECG interpretation of OMIs (that do not satisfy millimeter-based STEMI criteria):
  • Check out ECG Blog #337 — that reviews a case with focus on distinction between a "NSTEMI" vs an OMI.
  • Consider the 2 Audio Pearls at the bottom of this page.
  • Consider Figure-3 — which reviews some ECG findings to look for when you suspect an acute OMI in a patient who does not satisfy the millimeter-based STEMI criteria that I review below this Figure.

Figure-3: ECG findings to look for when your patient with new-onset cardiac symptoms does not manifest STEMI-criteria ST elevation on ECG.
= = = = =
KEY Note #1: Insistence in satisfying millimeter-based STEMI criteria before considering prompt cath with PCI (or thrombolytic therapy when access to 24/7 cath-capability is not available) — will miss at least 1/3 of all acute coronary occlusions. In a patient with new CP — attention to the ECG findings in Figure-3 may allow you to identify these patients with an acute OMI despite lacking STEMI criteria.
= = = = =
KEY Note #2: Loss of potentially viable myocardium is actually much greater than that implied in Key Note #1 — because even for patients in whom a "STEMI" is eventually recognized — by waiting until millimeter-based criteria are finally satisfied, the needed reperfusion therapy (PCI or thrombolytic therapy) is all-too-often delayed (often by many hours!)Time is critical! — as the greatest amount of potential myocardial-saving benefit occurs when reperfusion therapy is provided within the first few hours! (with the self-fulfilling prophecy that the outdated and inferior "STEMI-paradigm" gets perpetuated in the literature — because data will be recorded saying PCI was delivered "within minutes" of STEMI elevation [neglecting the clinical reality that OMI-criteria will often have been present hours earlier! ).
= = = = =
Note #3: See ECG Blog #318 — for clarification of T-QRS-D (Terminal QRS Distortion = my 2nd bullet in Figure-4).



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


How a "STEMI" is Defined:

I've excerpted the following Akbar and Mountfort's citation in StatPearls, 2024 — of ECG Guidelines for defining a "STEMI" from the AHA (American Heart Association)ACC (American College of Cardiology)ESC (European Society of Cardiology), and the WHF (World Heart Federation):
  • New ST-segment elevation of ≥1 mm at the J point in 2 contiguous leads (except in leads V2 and V3).

  • In leads V2 and V3:
    • ST elevation ≥2 mm for men >40 years of age.
    • ST elevation ≥2.5 for men ≤40 years of age.
    • ST elevation ≥1.5 mm for women.


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ECG Media PEARL #10 (10 minutes Audio) — reviews the concept of why the term “OMI” ( = Occlusion-based MIshould replace the more familiar term STEMI — and, reviews the basics on how to predict the "culprit" artery.



ECG Media PEARL #11 (6 minutes Audio) — Reviews how to tell IF the “culprit” (ie, acutely occluded) artery has reperfused, using clinical and ECG criteria.










Saturday, February 28, 2026

ECG Blog #520 — How Certain are You?


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)].

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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.

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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 in today's case that we can increase the statistical likelihood of VT 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 — this gives us 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?



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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 regular 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 atrial activity. 
  • To do this — I look to see what the shortest distance between 2 consecutive RED arrows appears to 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 using calipers 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 clearly be seen peaking out from the tail end of the QRS of beats #7 and 28 (ie, 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:
 The P waves represented by the colored arrows in Figure-4 are unrelated to neighboring QRS complexes. This tells us there is complete AV dissociation occurring throughout the long lead II rhythm strip — which proves that the rhythm is VT!
  • In my experience — AV dissociation is very much 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 accompanying often large-sized ST-T waves) are highly efficient at concealing underlying on-time P waves that are hidden within.

  • BOTTOM Line: The colored arrows seen in Figure-4 are convincing of AV dissociation — because they consistently occur thoughout the long lead II rhythm strip. 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 use of AV dissociation for assessing the etiology of a regular WCT rhythm — Review of ECG Blog #335 should prove insightful.
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Today's CASE Continues:
The patient in today's case is a middle-aged man with a history of hypertrophic cardiomyopathy. He was seen for new palpitations that occurred in association with today's presenting rhythm.
  • Paramedics on the scene cardioverted the patient. This worked momentarily to restore a normal rhythm — but soon after the WCT rhythm returned.
  • IV Amiodarone was started. The patient quickly improved — and vital signs stabilized. 
  • At this time — the repeat ECG shown at the bottom of Figure-5 was recorded. 


QUESTIONS:
  • How do you interpret the rhythm in the repeat ECG?
    • Does ECG #2 support our diagnosis of VT in the initial tracing?
 
Figure-5: The repeat ECG recorded after starting IV Amiodarone. The initial ECG is shown on top (with RED arrows highlighting AV dissociation from the underlying regular sinus P waves). 


The Rhythm in ECG #2:
The repeat ECG ( = the tracing at the bottom of Figure-5— shows a bigeminal rhythm, in which every-other-beat is a PVC.
  • Once again — the KEYs to interpreting the repeat tracing are to: i) Label the P waves in ECG #2; — and, ii) Determine if the P waves in ECG #2 are related to neighboring QRS complexes?

Note the following:
  • Regular P waves are seen in the repeat ECG throughout the long lead II rhythm strip ( = RED arrows in the bottom tracing in Figure-6). The rate of these P waves in the repeat tracing is slightly slower than it was in ECG #1.
  • Normal sinus rhythm conduction is seen in ECG #2 for all odd-numbered beats — as determined by the fixed PR interval before beats #1,3,5,7,9,11,13,15,17.
  • All even-numbered beats in ECG #2 are PVCs. The fact that on-time sinus P waves continue throughout the long lead II rhythm strip in this repeat tracing proves that beats #2,4,6,8,10,12,14,16 are PVCs — as is shown in the laddergram in Figure-7 ( = the only way for on-time sinus P waves to continue uninterrupted in Figure-7 — is for the even-numbered beats to originate from the ventricles, with retrograde conduction of these PVCs not reaching all the way back to the atria).
  • Finally — Note that QRS morphology of the premature wide beats in ECG #2 is identical to QRS morphology in each of the 12 leads of the initial ECG (thereby confirming our diagnosis of VT for ECG #1).

Figure-6: I've labeled P waves in the repeat ECG.

 

Figure-7: Laddergram of the repeat ECG.


CASE Conclusion:
  • The paramedic team transported the patient to the hospital. Referral was made to EP cardiology for consideration of an ICD (Implantable Cardioverter-Defibrillator).

 


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