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| Figure-1: The initial ECG in today's case — obtained from 60-something year old patient. (To improve visualization — I've digitized the original ECG using PMcardio). |
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| Figure-2: The |
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| Figure-3: The |
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| Figure-4: The |
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| Figure-5: The |
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| Figure-6: I have adapted this figure from the September 23, 2011 post in Dr. Venkatesan's Cardiology Blog. It explains how "polymorphic" VT might arise from a single venricular focus, rather than from multiple sites in the ventricles (See text). |
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Acknowledgment: My appreciation to Fardeen Baray and Hameedullah Ahmadzai (from Kabul, Afghanistan) for the case and these tracings.
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Fardeen Baray — FB Messenger (5/9/2026)
ACKNOWLEDGE:
Fardeen Baray and Hameedullah Ahmadzai (from Kabul, Afghanistan)
— I must add possibility of multiple exit sites = Blog #231 !!! —
— "Why 2 Morphologies?" —
NOTE — I think I will only show the initial ECG!
THE CASE:
Hello sir Hope this message finds you well This ECG has been sent to me without saying anything about patient symptoms Could please comment on this tracing. The following in my comment The patient history will help us a lot in dx. This is an interesting and electrophysiologically complex ECG. Clinically correlated history and serial ECGs would be very helpful. The ECG appears to show a regular wide-complex rhythm with a bigeminal/alternating pattern and no clearly identifiable sinus P waves. Differential considerations include AIVR, accelerated junctional rhythm with underlying RBBB, or competing junctional and ventricular pacemakers with fusion phenomena. The inferior ST elevations raise concern for acute inferior ischemia/reperfusion, which would support AIVR as a likely mechanism.
MY REPLY:
Hi. Fascinating! Clearly alternating polarity in this fairly slow ventricular rhythm. The only suggestion of atrial activity that I see is possible retrograde P waves in some chest leads. To me — this looks like BiDirectional VT! — a RARE rhythm — but can occur! See my ECG Blog #436
(https://ecg-interpretation.blogspot.com/2024/06/ecg-blog-436-bigeminy-or-alternans.html ) — Acute ischemia/MI is one possible etiology — and that DOES seem likely with what looks like acute ST elevation and depression that "shouldn't be there" in a number of leads! Let me know what happens! If you can give me follow-up — might be a good one for an ECG Blog! —
FARDEEN REPLY:
Thank you very much sir for your valuable comment. I will share patient info once I received. The heart rate in this tracing is less than 100 that’s why we mainly focused on AIVR and specifically competing AIVR and accelerated junctional rhythm. What’s your comment about this competing AIVR and Accelerated junctional rhythm
MY REPLY:
Yes the rate of the rhythm is slow for "VT" — and it is mainly because of the differing QRS morphology that I thought this was more of a"BiDirectional Ventricular Rhythm" (whether you call it "VT" vs "bidirectional AIVR" I think is a matter of preference). True bidirectional VT is RARE! — so I don't know that any rate limits have been agreed on — and if that is what this is, the concept differs from the usual "AIVR" which is an escape rhythm (and one that often occurs with reperfusion of an uncomplicated acute MI). So — the R-R interval varies a bit, but not really every-other beat — so I cannot rule out some form of alternating aberrant conduction. But the reason I don't favor that is that QRS morphology really is not consistent with any form of known conduction defection (not truly rbbb + lahb or lphb). Now IF the baseline ECG is very abnormal, then it could be alternating forms of aberrant conduction. As to AIVR + junctional — note the 2 alternating morphology forms (within the dotted RED and dotted GREEN rectangle) — and BOTH show very wide complexes that do not conform to either lahb or lphb morphology ==> I think more like both being of ventricular etiology. I cannot prove this is "bidirectional VT" — and I count on the fingers of my hands how many times I've seen cases of this outside of textbooks — so it is NOT something that is often seen, therefore experience would seem quite limited — but I agree that it looks like there is "extra" ST elevation and "extra ST depression in some complexes, which increases suspicion of recent/ongoing acute MI (as we both noticed) — and perhaps the relatively slow ventricular rate IS a manifestation of "bidirectional AIVR" because of spontaneous reperfusion following an acute MI .... BOTTOM LINE — I think more follow-up, more details, prior and later tracings will be needed to "put all the pieces together" — but the above are my thoughts re what may be going on at this point —
FARDEEN REPLY:
Some new info about the patient is that patient has been 47 years old obese patient without significant past history, currently suffering from acute crushing chest pain which ended up to to patient collapse and according to patient’s relatives with low spo2 and undetectable BP most probably cardiogenic shock and pulmonary edema. Patient underwent cor Angio plus pci during which patient collapsed and ended up cardiac arrest. Patient has been resuscitated after giving several shocks according to patient attendance. Patient is currently unconscious under ventilator. By the time patient’s other ECG tracing is sent to me I will share them with you.
MY REPLY:
Thanks for the follow-up! Any idea about WHEN this ECG that you sent me was done with respect to the above history. In any case — the scenario to me is consistent with a bidirectional "slow" VT as a result of ischemia/acute MI and shock state ...
FARDEEN REPLY:
According to the patient attendance it was taken before PCI.
MY REPLY:
That helps — as it goes along with this bidirectional rhythm as an indicator of acute ischemia ...
FARDEEN REPLY:
Some updates about the patient is that she is still under vent. The above ECG is very first tracing when patient was complaining of chest pain.
This last ECG is taken after PCI.
MY REPLY:
Hi. THANKS for the follow-up. What did the cath show??? Unfortunately — the very first ECG is too light for PMcardio to improve the image. Can you get a better quality original? It's OK if not since it might be better for the case to just show the tracing you sent me first — and the post-PCI tracing (as I put these 2 tracings together on the attached). So that very first tracing when the patient had CP (Chest Pain) really does NOT show much at all ... The attached figure shows the tracing you sent me + the post-PCI tracing. I think both QRS morphologies on the TOP tracing are different enough from the post-PCI tracing as to confirm that the rhythm you sent me was a bidirectional ventricular rhythm — presumably due to ischemia, and which corrects after PCI. Great case! So I may write this case up. If so — Would you like me to acknowledge you, or leave it anonymous? Could you tell me the city and country from where you are from (as I like to include that information). It may be a while until I publish this, as I have other cases to go before. THANKS again! —
FARDEEN REPLY:
Cath showed the lcx to be total and had thromb shift to the lad.
This wasn’t my patient I will get permission from the one who sent me these tracings.
MY REPLY:
I can acknowledge your colleague and also you if you like. Just let me know — :)
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FARDEEN REPLY on May 11 !!!
ACKNOWLEDGE:
Fardeen Baray and Hameedullah Ahmadzai (from Kabul, Afghanistan)
Fardeen — I am an associate professor of Cardiology at Kabul University of Medical Sciences, Hameedullah Ahmadzai is a Cardiologist.
Sir, could AIVR with alternating exit/fusion patterns be considered a possible alternative diagnosis in this case, perhaps to further strengthen the publication? I truly appreciate your hard work and your efforts to share knowledge. I have personally learned a great deal from your insightful comments and, of course, from your weblog as well. I would highly recommend your work to both senior and junior colleagues alike.
= = = =
MY REPLY:
Hi. Thanks for the info. It may be a while ... but I'll let you know when I publish this — and I'll acknowledge Fardeen Baray and Hameedullah Ahmadzai (from Kabul, Afghanistan).
Good point about about AIVR with alternating exit sites! I review this concept in my ECG Blog #231
(https://ecg-interpretation.blogspot.com/2021/06/ecg-blog-231-what-is-this-bizarre.html ) from which the attached figure comes from. It would seem impossible to rule out the possibility of different (alternating) exit sites — but I will be sure to add this as a possibility.
GREAT corresponding with you! Take care — :)
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ECG Blog #436
https://ecg-interpretation.blogspot.com/2024/06/ecg-blog-436-bigeminy-or-alternans.html
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- The patient presented to the ED (Emergency Department) for an episode of syncope. He developed cardiac arrest shortly after the ECG in Figure-1 was recorded.
- How would YOU interpret the ECG in Figure-1?
- What is the most likely cause of this arrhythmia?
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| Figure-1: The initial ECG in today's case. (To improve visualization — I've digitized the original ECG using PMcardio). |
- There are 2 different QRS morphologies — both of which clearly manifest a wide QRS complex when this rhythm is viewed in certain leads. Thus, although one of these QRS morphologies looks narrow in lead V3 — a glance at leads III, aVR, aVL, V1 and V2 confirms that the QRS is wide!
- NOTE: Although QRS morphology from one-beat-to-the-next looks similar in certain leads (ie, in leads aVR, V4,V5,V6) — there can be no doubt about the presence of 2 distinct QRS morphologies when one looks at leads I, III, aVL, aVF — and leads V1,V2,V3.
- The overall rate of the rhythm in Figure-1 is fast (at least 150/minute).
- There are no P waves.
- And, the patient is older (ie, prone to reduced renal function) — and he is taking Digoxin.
- As discussed in ECG Blog #231 — Bidirectional VT is a special form of VT, in which there is beat-to-beat alternation of the QRS axis. This unique and very uncommon form of VT is distinguished from PMVT (PolyMorphic VT) and from pleomorphic VT — because a consistent pattern (ie, alternating long-short cycles) is usually seen throughout the VT episode. As implied in its name, there are 2 QRS morphologies in bidirectional VT — and they alternate every-other-beat (CLICK HERE — for this case report Review by Femenia et al on Bidirectional VT in a patient with CPVT = Catecholaminergic Polymorphic VT).
- KEY Point: There are a limited number of causes of Bidirectional VT — with the 2 most common causes being Digoxin toxicity and CPVT. Given that today's patient was taking Digoxin — Digoxin Toxicity was immediately suspected as the most likely cause.
- Since Digoxin is primarily renally excreted — older age, that is commonly associated with reduced renal function, would predispose to developing Digoxin toxicity.
- Digitalis toxicity.
- CPVT (Catecholaminergic PolyMorphic VT).
- Acute myocardial ischemia.
- Familial hypokalemic periodic paralysis.
- Cardiac Sarcoidosis.
- Primary Cardiac Tumors and/or Cardiac Metastasis.
- Andersen-Tawil Syndrome ( = Long QT Syndrome, Type 7).
- Acute Myocarditis.
- Certain drug overdoses (Aconitine poisoning, severe caffeine poisoning).
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Acknowledgment: My appreciation to Hafiz Abdul Mannan Shahid (from Lahore, Pakistan) for the case and these tracings.
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Related ECG Blog Posts to Today’s Case:
- ECG Blog #36 — Reviews irregular wide tachycardias (with distinction between Torsades de Pointes vs Polymorphic VT discussed in Figure-3 in this post).
- See My Comment in the June 1, 2020 post in Dr. Smith's ECG Blog — for review of Pleomorphic VT.
- ECG Blog #231 — for review on the types of VT (including monomorphic — polymorphic — pleomorphic — and bidirectional VT).
- Bidirectional VT: Challenges and Solutions (Almarzuqi et al — Vasc Health Risk Mgmt 18:3997-406, 2022).
- Pleomorphic VT and Sudden Cardiac Death — Editorial by Liu and Josephson on potential mechanisms to explain the ECG appearance of Pleomorphic VT.
- Case Report on BiDirectional VT — by Femenia et al on this patient with BiDirectional VT from CPVT (Catecholaminergic Polymorphic VT).
- ECG Blog #197 — Reviews the concept of Idiopathic VT (including recognition and treatment of Fascicular VT and RVOT VT).
- Multifocal vs Polymorphic VT — September 23, 2011 post from Dr. S. Venkatesan's insightful and user-friendly Cardiology Blog (from which I adapted his figures to derive my Figure-3).
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ECG #231
https://ecg-interpretation.blogspot.com/2021/06/ecg-blog-231-what-is-this-bizarre.html
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The 12-lead ECG shown in Figure-1 was obtained from a previously healthy 55-year old man who presented to the ED (Emergency Department) with shortness of breath, altered sensorium and hemodynamic instability.
- WHAT are the diagnostic possibilities for the rhythm?
- What do you feel is the most likely rhythm diagnosis?
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| Figure-1: Presenting ECG from a 55-year old man with shortness of breath, altered sensorium and hemodynamic instability (See text). |
MY THOUGHTS on ECG #1:
My initial impression on looking at the ECG in Figure-1 — was that this irregular, wide rhythm was probably rapid AFib (Atrial Fibrillation), with a mixture of PVCs (Premature Ventricular Contractions) and aberrant conduction of supraventricular impulses.
I Changed My Mind on taking a 2nd Look at this tracing:
- I saw no sign of atrial activity.
- I thought all 25 QRS complexes on this tracing were probably ventricular in etiology (Figure-2). Although the QRS does not look overly wide in some leads — as you follow each of these 25 beats down the page from lead I at the top (looking in each of the 11 simultaneously-recorded leads below lead I) — the QRS is revealed to be either definitely wide in other leads — or — to manifest a QRS morphology strongly suggestive of a ventricular etiology (ie, the all-negative, widened complexes in lead V6 for beats #4,5; 8; 11, 12; 14,15; and 21 are ~99% likely to be ventricular in etiology).
- While I can't rule out the possibility that there might be a few supraventricular "capture" beats in Figure-2 — I believe it fair to say that more than 20 of the 25 beats in this tracing are ventricular in etiology.
- Unlike AFib — there does appear to be a "pattern" to the rhythm in Figure-2 (Doesn't the shape and relative timing of beats within the 2 YELLOW and 2 WHITE rectangles in Figure-2 look surprisingly similar?).
- BOTTOM Line: Despite irregularity of the rhythm and variability in QRS morphology — I thought the rhythm in Figure-2 had to represent some form of VT (Ventricular Tachycardia).
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| Figure-2: I have numbered the beats in ECG #1. Doesn't it look like there is some kind of repetitive group pattern in successive beats? (Look within the 2 YELLOW and 2 WHITE rectangles at sequential beats in the long lead V6). |
VT Terminology:
Before going further — it may help to review a number of terms that have been used to describe the morphologic appearance of various forms of VT. These include:
- Monomorphic VT — in which there is a similar (if not identical) QRS appearance throughout the episode of VT.
- PolyMorphic VT (PMVT) — in which QRS morphology and/or axis continuously changes from one beat-to-the-next throughout the episode of VT. PMVT is not a regular rhythm — and it is often quite irregular. When PMVT is associated with a long QT interval — the rhythm is then defined as Torsades de Pointes (See ECG Blog #36 for more on distinction between Torsades vs PMVT).
- Pleomorphic VT — in which more than a single QRS morphology is seen during an episode of VT. Pleomorphic VT differs from PMVT — because QRS morphology is not changing from one beat-to-the-next. Instead, one QRS morphology will be seen for a number of beats — and then another morphology may take over and continue for another series of beats. Several different morphologies may be seen. (For more on Pleomorphic VT — Please SEE My Comment in the June 1, 2020 post in Dr. Smith’s ECG Blog).
- Bidirectional VT — in which there is beat-to-beat alternation of the QRS axis. This unique and very uncommon form of VT distinguishes itself from PMVT and pleomorphic VT — because a consistent pattern (ie, alternating long-short cycles) is usually seen throughout the VT episode. As implied in its name, there are 2 QRS morphologies in bidirectional VT — and they alternate every-other-beat. (CLICK HERE — for this case report Review by Femenia et al on BiDirectional VT in a patient with CPVT = Catecholaminergic Polymorphic VT).
WHY CARE about QRS Morphology with VT?
Classification of the morphologic type of VT may provide clues to etiology, outcome and treatment.
- Monomorphic VT may occur in patients with or without underlying structural heart disease. Because the ventricular activation sequence is constant in monomorphic VT (which is why all beats look the same) — successful treatment (either by medication or cardioversion) is generally easier to accomplish.
- The occurrence of monomorphic VT in a patient without underlying structural heart disease (and without QT prolongation or metabolic/electrolyte abnormalities) — is known as Idiopathic VT. The “good news” — is that long-term prognosis of patients with idiopathic VT tends to be excellent (See ECG Blog #197 for more on Idiopathic VT).
- As noted earlier — Bidirectional VT is extremely uncommon. Think of digitalis toxicity and catecholaminergic polymorphic VT as potential etiologies in which you are more likely to see bidirectional VT.
- Pleomorphic VT is also uncommon, and less well known than the other morphologic forms of VT. Patients with pleomorphic VT generally have significant underlying structural heart disease. A number of mechanisms have been proposed to explain the pattern of pleomorphic VT, in which there may be one or more runs of VT with a given similar QRS morphology — that is then punctuated by runs of VT with 1 or more other QRS morphologies. Potential mechanisms for explaining pleomorphic VT are complex — and include the possibility of: i) a single VT circuit with more than a single exit site; ii) the presence of more than a single VT circuit; and/or, iii) shifting conduction properties that alter the activation sequence (Liu & Josephson — Circ Arrhythm Electrophyiol 4:2-4 2011).
PolyMorphic VT (PMVT) — is divided into 2 groups, depending on whether the preexisting QT interval is prolonged.
- The occurrence of PMVT in association with baseline QTc prolongation — is defined as Torsades de Pointes. Torsades often has a multifactorial etiology (ie, drug-induced, electrolyte depletion, CNS disturbance and/or other underlying disorder that may predispose to QT lengthening). KEY aspects of treatment include IV Mg++ (often at high dose) + finding and “fixing” the cause of the long QTc.
- In contrast — PMVT without QT lengthening most often has an ischemic etiology. Although IV Mg++ is also indicated as initial treatment of PMVT with a normal QT — it is clearly less likely to respond to IV Mg++, than when the QT interval is prolonged. Instead, antiarrhythmic drugs such as amiodarone or ß-blockers may be needed — and/or treatment targeted to correcting ischemia.
COMMENT on Today's Case:
What I found especially interesting about the rhythm in Figure-2, is that unlike the complete variability in QRS morphology and R-R intervals that is usually seen with PMVT — there seemed to be a distinct, repetitive pattern in several parts of this tracing.
- That said, given lack of atrial activity and numerous different ventricular QRS morphologies — I thought the rhythm in today's case to be most consistent with Polymorphic VT.
- Clinical details on this patient were scarce — but there was no history of medication use or toxic ingestion.
My thoughts as to why there may be a repetitive pattern in parts of the rhythm in from today's case — are illustrated in Figure-3, which I adapted from the September 23, 2011 post in Dr. Venkatesan's Cardiology Blog.
- Although one might expect PMVT to originate from multiple sites in the ventricles — much (if not most) of the time — this is not what happens. Instead — it is more common for PMVT to originate from a single ventricular focus (despite significant variation in QRS morphology that may sometimes be seen from one beat-to-the-next).
- As suggested in Figure-3 — the physiologic explanation for why this may happen, is that the polymorphic VT focus may travel over a different path in its exit from the myocardium.
- Irregularity of PMVT may be explained by variation in conduction times for the various exit paths.
- The "repetitive pattern" that I suggest is present (within the YELLOW and WHITE rectangles drawn in Figure-2) — may be the result of a somewhat organized "rotation" over a series of potential exit paths.
- PEARL: As one might imagine — most PMVT rhythms are hemodynamically unstable, with tendency toward rapid deterioration to VFib. That said — Dr. Venkatesan makes the clinically important point that on occasion — some PMVT rhythms are surprisingly well tolerated! This could be the result of a "competition" between the different foci and/or exit sites that serve to prevent any one malignant focus from predominating and precipitating deterioration to VFib. To paraphrase Dr. Venkatesan, "One VT focus may act like a natural anti-tachycardia pacing device, that serves to terminate a VT from another focus".
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| Figure-3: I have adapted this figure from the September 23, 2011 post in Dr. Venkatesan's Cardiology Blog. It explains how "polymorphic" VT might arise from a single venricular focus, rather than from multiple sites in the ventricles (See text). |
FOLLOW-UP to Today's Case:
Unfortunately — the rhythm in Figure-2 deteriorated, and cardiac arrest was called. The patient could not be resuscitated. I believe this unfortunate clinical course supports our presumption of PMVT as the etiology of the rhythm in today's case. Further information on the case was not available — so we never learned the cause of this malignant rhythm.
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Acknowledgment: My appreciation to Hafiz Abdul Mannan Shahid (from Lahore, Pakistan) for the case and these tracings.
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Related ECG Blog Posts to Today’s Case:
- ECG Blog #36 — Reviews some irregular wide tachycardia rhythms (with distinction between Torsades de Pointes vs Polymorphic VT discussed in Figure-3 on this post).
- See My Comment in the June 1, 2020 post in Dr. Smith's ECG Blog — for review of Pleomorphic VT.
- Pleomorphic VT and Sudden Cardiac Death — Editorial by Liu and Josephson on potential mechanisms to explain the ECG appearance of Pleomorphic VT.
- Case Report on BiDirectional VT — by Femenia et al on this patient with BiDirectional VT from CPVT (Catecholaminergic Polymorphic VT).
- ECG Blog #197 — Reviews the concept of Idiopathic VT (including recognition and treatment of Fascicular VT and RVOT VT).
- Multifocal vs Polymorphic VT — September 23, 2011 post from Dr. S. Venkatesan's insightful and user-friendly Cardiology Blog (from which I adapted his figures to derive my Figure-3).
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